Sai

is an Anbu of Konohagakure. Raised as a member of Root, Sai has no emotions and has difficulty connecting with others. When he is added to Team Kakashi as a replacement for Sasuke Uchiha, he begins to learn about people's feelings and tries to develop himself by forming bonds and developing emotions.

Background
Sai was orphaned as a child and recruited into Root, a secret branch of the Anbu. There he was raised and conditioned to have no personality, personal connections, or a name; "Sai" being given to him for the purposes of joining Team Kakashi. Though largely successful in this regard, Sai retained an interest in art. When Shin, an older Root member, discovered Sai's drawing ability, he encouraged Sai's talent and they became very close.

Over time, Sai came to think of Shin as an older brother and looked up to him. Unfortunately, Sai and Shin were supposed to fight to the death by Root regulations, in a final step to eradicate emotions. Before that happened, however, Shin died of an unnamed illness and Sai's Root training suppressed most of the memories he had of him. In the anime, Sai and Shin were forced to fight by Danzō Shimura but Shin died before the battle could be finished. Shin told Sai to report to Danzō that he killed him in battle and before succumbing to his illness, told his brother that he had to suppress his feelings and that he should live for the both of them.

Before Shin's death, Sai created a picture book that would depict all the opponents they faced and illustrate the feelings that they shared for each other. Sai organised the book so that his and Shin's portraits would be located at opposite ends of the book, and in the centre pages would be a picture of them holding hands. Some time after the loss of Shin, Sai forgot that this was his intention, and the picture book was left unfinished, though he could never bring it upon himself to discard the book.

During his time in Root, Sai was ordered to eliminate a large number of individuals that posed a threat against Konoha. The last assassination he performed was of Unmo Samidare. In an attempt to gain a powerful fūinjutsu after seeing the Third Hokage sacrifice his life in an attempt to defeat Orochimaru, Danzō supervised Sai while he learned how to use the Sealing Technique: Tiger Vision Staring Bullet, noting that it would be dangerous as he would have to use "emotional energy" in order to make the technique stronger. Sai struggled greatly with this endeavour as it conflicted with his training and, consumed by negative emotions, his training was seemingly left incomplete.

Personality
When first introduced, Sai was distinguished by his total lack of emotion which he often masks with a false, cheerful, yet transparent façade. After much mental conditioning and training while in Root, Sai had suppressed almost all of his emotions, laying all of his loyalty to whoever commands him, and thus making it easier for him to accomplish dangerous, unpleasant, or unethical missions. Due to this training and his lack of social experience and personal initiative, Sai has great trouble in understanding how bonds between people can motivate others. He often showcases this confusion after thinking about why Naruto would go so far to save Sasuke, a traitor, even though Naruto had not been ordered to do so.

Sai's social awkwardness tends to get people angry, because he often speaks without considering his words and their effects on people. This was due to his inability to realise the difference between a rude statement and a true statement. Sai had read somewhere in a book that giving somebody a nickname would bring you closer to that person and develop your friendship, this resulted in Sai hurting Sakura Haruno's feelings, because he called her "ugly", stating the first true character trait that came to his mind. This also nearly led to enraging Chōji, while eating barbecue with Team Asuma and Team Kakashi he nearly called him "fatso" before Naruto covered his mouth before he could finish. Realising he was offending people by saying characteristics that came to his head, Sai decided to take a different approach by saying the opposite of what came into his head. In this way, at the same event Sai called Ino "gorgeous" (although he truly meant to call her "ugly"), much to Ino's surprise, Naruto's relief, and Sakura's outrage.

After spending more time with Team Kakashi, Sai comes to appreciate bonds, particularly the bond that exists between Naruto Uzumaki and Sasuke Uchiha, though Sai would come to have his doubts about Sasuke when he began to commit crimes on an international scale, which Naruto would suffer for. This causes him to break out of his emotionless shell and start to remember the times he had with his own "brother", Shin. In doing so, Sai was able to start giving genuine smiles. Wanting to experience personal bonds for himself, Sai sets out to make as many friends as he can. However, since he is learning most of this out of books and by trial and error, he often accidentally ends up offending people with his nicknames and conversation. He has come to develop a more genuine, pleasant and thoughtful personality, while also showing signs of more emotion, such as enthusiasm and occasionally nervousness. After his first time with Team Kakashi, Sai is seen being friendly towards others, helping companions when they need it, referring to peers kindly, and having fun in social situations. He later appeared to show genuine anger while explaining to Sakura about Naruto's feelings for her and later when she lied to Naruto about the predicament with Sasuke and trying to use a fake confession to get him to give up on Sasuke. The greatest change in his personality, however, came after he encounters his reincarnated brother. When Shin is used as a living bomb by Deidara, Sai became truly enraged for the first time and attacked Sasori and Deidara mercilessly, showing genuine rage on his face. Sai also displayed genuine sadness, shedding tears when his brother was freed from the technique and disappears.

Sai is very observant, and is always focused on his missions. He pays a lot of attention to detail, allowing him to quickly notice if something is not as it appears, as shown from how he easily sees through Yamato's tricks. This awareness spans beyond the trials of duty, as Sai was later quick to understand the nature of Naruto's inner suffering without Naruto even telling him. What he failed to understand, however, was that Naruto was not trying to save Sasuke just for Sakura. Sai holds Naruto in high regard, and tries to assist Naruto whenever he's going through hardships. This bond with Naruto led Sai to start to understand camaraderie, and by the Fourth Shinobi World War, he realised he understood it as he, Rock Lee, and various others went to assist Naruto as he fought against Tobi. Growing up over the following the years, Sai came to truly understand compassion and love, as he ultimately formed a family with Ino. He has also begun training his son in his artistic-ninjutsu, finding humor in Inojin's cruder drawing.

Appearance
Sai has short, straight black hair, and dark eyes which contrast with his translucent-looking pale skin. He is usually seen carrying a small backpack with his brush, scrolls, and ninja ink in it. He wears a short black-and-grey jacket with red straps — as customary of all Root members, to most likely show his allegiance to the organisation. He also carries a tip-less tantō on his back. The rest of his outfit consisted of a high-collared midriff shirt, black pants, shinobi sandals and gloves with his index and thumb fingers exposed, most likely to facilitate the use of his drawing based techniques. When first seen with Team Kakashi, his jacket has a long right and short left sleeves. He had Danzō's cursed seal on the back of his tongue until Danzō's death, which caused it to disappear. Naruto, Sakura, and Ino said he physically resembled Sasuke, despite his shorter hair and paler skin-tone. When he's not on missions, Sai wears a casual outfit consisting of a long-sleeve shirt with a high collar, matching pants, and his regular shinobi sandals. This outfit was first depicted as being purple in colour and later, navy blue. He doesn't wear his forehead protector or gloves with this outfit. In the anime, when Sai uses the Sealing Technique: Tiger Vision Staring Bullet and his negative emotions surface because of his use of "emotional energy", his eyes turn a translucent red colour and his sclerae turn black. This is apparently, as when Danzō countered the symptoms, ink splattered from Sai's body.

In The Last: Naruto the Movie, two years after the Fourth Shinobi World War, Sai's hair grew longer with his bangs framing his face. His attire is similar but both sleeves of his shirt, which is now completely black, are long, and his shinobi sandals reach more above his calves. He also has a large scroll strapped horizontally to his back.

Many years after the Fourth Shinobi World War, Sai's jacket now is long enough to cover his entire upper body, with both sleeves long. He continues wearing a scroll on his back and long sandals, but his pants are slightly different.

Abilities
As a member of Root, Sai is a highly capable ninja, considered by Danzō himself to be the strongest member of his generation. Danzō even had enough faith in Sai's abilities to task him with single-handedly killing Sasuke Uchiha. During the Fourth Shinobi World War, Sai's skills had increased to the point where he could defeat Deidara and Sasori at the same time, leaving them to be sealed. Two years after the war, his skills proved great enough to defeat multitudes of Toneri Ōtsutsuki's puppets with ease.

Nature Transformation
Sai also has proficient skill in Earth Release able to use the nature transformation to conceal himself underground without disrupting the surface of the earth. He can also use the elements of Fire, Water, and Yang.

Ink Techniques
Sai's most notable talent is his skill as an artist, and he claims to have drawn thousands of pictures. Despite the great quantity and magnitude of the things he has drawn, he has never given any of his works a name, his lack of emotion making it impossible for him to form a significant enough attachment to his art to give titles. Even so, Sai's drawing talent is also the source of his technique, known as Super Beast Imitating Drawing.

To be able to execute his Super Beast Imitation Drawing technique, Sai carries around a specialised custom scroll to draw on, the scroll's roller has compartments for Sai's ink brush and to hold a supply of ink. A distinct advantage of this technique is that he can perform it with a single hand, leaving the other free for enemy counter-attacks. In the anime, Sai gets his ink from a supply store, which he says is the ink that works best for his Super Beast Imitation Drawing techniques. By infusing his chakra into the ink beforehand and drawing objects with a brush on his scroll, which he can do very quickly, Sai is able to bring his creations to life by animating the ink directly off the page. These creations grow to life-size once they have been brought to life — similar to Deidara's explosive clay constructs.

Sai typically creates giant birds for long range transport for himself or others, and lion-like monsters or giants for attack, or objects like umbrellas for everyday use. He can create snakes and use them as strong bindings on enemies, or mice to quickly scout an area. Sai can make clones of himself for reconnaissance. For discreet communiques when he is undercover, Sai is able to turn the words he writes into small animals, allowing them to travel to their intended target unnoticed. He has also demonstrated the ability to create large scale drawings as shown during the battle of the two ambush squads; he created two large human beings which resembled the. These had enough physical strength to completely destroy Deidara's clay bird as well as send him along with Sasori plummeting to the ground. Sai can create explosive tags with his ink technique. He can draw long lines of tags attached to small birds, allowing him to bombard enemies from the air.

Fūinjutsu
As noted by Kakashi, Sai is one of Danzō's prized soldiers and as such, his Root training also included learning fūinjutsu. His sealing technique allows him to trap people within his paintings by drawing a tiger on a large scroll with a giant paint brush. Since it takes time to draw the tiger, he needs allies to protect him while in battle. In the anime, it is stated that Sai uses "emotional energy" to bolster the technique. This is a double-edged sword as Sai becomes susceptible to his negative emotions.

Taijutsu
Despite not being his speciality, Sai has shown to be proficient in taijutsu. He was able to react and block Naruto's attempt to stab him with a kunai very easily with his tantō. He also was able to subdue Kabuto Yakushi very easily and block Sasuke Uchiha's attempt to stab Naruto, with Sasuke commenting that he blocked the attack in the most appropriate manner. During the Fourth Shinobi World War, he was able to break Shin's neck with a flying knee kick in mid-air. Even without the use of his tantō, he has shown great skill with a bladed weapon and was able to fight equally with an oponent wielding a larger weapon.

Other Skills
As a Root Anbu, Sai has keen observation skills and is also skilled in kenjutsu, wielding a tantō in battle. He is also very proficient with the Body Flicker Technique, and is capable of surprising even highly-skilled shinobi with it.

Tenchi Bridge Reconnaissance Mission
Sai was assigned to join Team Kakashi by his superior Danzō to assist in meeting with a spy in Orochimaru's ranks to find out about Sasuke Uchiha. Sai was confrontational with his new team-mates upon their first meeting, exasperating both Sakura and Naruto. On their way to the rendezvous point, Sai once again aggravated them, questioning Naruto's manhood and insulting Sasuke. The latter caused Sakura Haruno to punch him in anger. As they continued on to the meeting point, Sai questioned why Naruto was loyal to a traitor like Sasuke, to which Naruto stated he was not a traitor, but a friend. Upon reaching the designated meeting place, Yamato went ahead disguised as Sasori so that he could meet the spy. When the spy, Kabuto Yakushi, arrived with Orochimaru to kill Sasori, Sai, Naruto, and Sakura were called in for help.

When Naruto and Orochimaru began fighting, Sai left the rest of the team to begin his real mission. He briefly observed Naruto's fight with Orochimaru, unconcerned with the danger he left Yamato and Sakura in, and approached Orochimaru after he had repelled Naruto with a proposition from Danzō. Orochimaru accepted, and Sai accompanied him and Kabuto back to their hideout. Once arrived at Orochimaru's hideout, Sai was introduced to Sasuke, who had been training under Orochimaru for the past two-and-a-half years. When Sai mentioned that he might get along better with Sasuke than he did Naruto, Sasuke temporally traps Sai within a genjutsu which startles Sai to the ground due to the amount of fear it gave his emotionless self. He was led to his own room afterwards by Kabuto, who locked Sai in upon leaving. Soon afterwards, Team Kakashi tracked Sai down and confronted him about his real mission. Having been caught, Sai explained that he had been assigned to ally with Orochimaru on Danzō's behalf so that the two may join forces in destroying Konohagakure.

Disgusted by the ramifications of this plan, Team Kakashi restrained Sai before setting out to find and retrieve Sasuke. Sai, however, doubted their success, stating that Sasuke no longer cared about them. Naruto, in response, stated that he also used to hate Sasuke, but over time he had formed a bond with Sasuke through their shared experiences, and as such he would do whatever it took to bring Sasuke home. Naruto's dedication to retrieving Sasuke struck a chord with Sai, who was left without words as a result. When Kabuto arrived and freed Sai, Sai instead helped them capturing Kabuto, hoping to accompany Naruto to find out more about bonds. Naruto and Sai split away from Sakura and Yamato to go looking for Sasuke. They were soon found by Orochimaru, and as a result, Naruto distracted him so that Sai could have a chance to scout on ahead. When Orochimaru retreated and Naruto reunited with Sakura and Yamato, Yamato went through the belongings that Sai had left behind. In doing so he discovered Sai's actual mission: to kill Sasuke as a traitor to Konoha.

Team Kakashi raced through the base to find and stop Sai, but Sai had already found Sasuke. Sai, however, truly had a change of heart, and instead, tried to capture Sasuke in order to protect his bond with Naruto. Irritated by Sai's reasons for bothering him, Sasuke attacked Sai, drawing the rest of the team to their location. When they found out what Sai was trying to do, they all teamed up to restrain Sasuke. Although Sai was able to land a successful attack, Sasuke's abilities were too much for them and he prepared to kill them all. He was soon stopped by Orochimaru and Kabuto, who convinced him to spare the team before leaving. Defeated, Team Kakashi returned home. Sai requested that he be allowed to stay as a part of the team and, with Danzō's approval, began to spend time with his new friends. Upon returning to Konoha and failing their mission, Sai began reading about relationships in the hopes of making some for himself.

Twelve Guardian Ninja
In the anime, Team Kakashi are sent on a mission concerning the Fire Temple. When the other party didn't meet the group, they decided to split into two groups. He stayed behind with Naruto while Yamato and Sakura went to search for the monks. His weird actions to try and build a stronger friendship with Naruto creeped him out and Naruto fled away from him. After re-grouping with Yamato and Sakura who found the monks, Sai witnessed Sora, a monk-in-training, fighting Naruto. This turned out to be a misunderstanding on the behalf of Sora thinking Naruto was trying to invade the temple.

After clearing up the confusion, the monks led Team Yamato to the Fire Temple. Upon reaching the temple, the monks explained to the team the situation regarding the sacred tombs' mysterious disappearance. News that another tomb was robbed reached the temple and Team Kakashi, accompanied by Chiriku and Sora, moved out to find the perpetrators. They soon spotted four other tombs moving across a field by themselves, heading up a cliff where four ninja lied. Fudō, one of the enemy ninja, quickly used an earth technique to create a rocky canyon maze, which separated Team Kakashi and Sora. Using an ink bird he tried to escape but was ultimately trapped inside. He was confronted by Fuen who mocked him for not being able to escape. Sai aware that the enemy knew the area, attempted to retreat and plan. Though he did get away, the enemy had the blue prints to the area and knew exactly where he went off to and tried to kill him. Some time after, he found and saved Sakura from a surprise attack from a giant spider. He managed to kill it, however, getting his arm injured in the process and Sakura tended to it. After the two had met up with Yamato, they found Naruto being drained of his chakra by a kiss from Fūka. They tried to help but were trapped by Fuen and Fudō. The cave soon collapsed and everyone scattered to safety.

When the group returned to the village, Sora went with them. While Sai left to take a rest, Naruto introduced Sora around the village per Sakura's request. Later, Sai, looking through the hospital window, saw that the village was being attacked by a technique used by Fudō and his fellow members. After sneaking out, he helped Asuma fight Kazuma, enabling Asuma to finish him off. The invaders were dealt with and Sora departed from Konoha.

Akatsuki Suppression Mission
Sai and the rest of team Kakashi were later sent as backup for Team 10 during their battle with Akatsuki. Because Shikamaru Nara was separated from the rest of the group, Sai and Sakura were sent to his aid, though upon arrival they found that Shikamaru had already defeated his opponent. Sai returned with everyone else to Konoha, having not taken part in the battle. Because Naruto was injured during the battle, he has difficulty eating when they got back. Sai, wanting to ameliorate their friendship, attempted to feed Naruto which angered him since he had wanted Sakura to feed him and Sai had interrupted her doing so. Neither has their way as Kakashi himself took up the task of feeding Naruto instead.

Three-Tails' Appearance
In the anime, Sai was placed on Team One along with Kakashi, Shino and Naruto. His team's duty was to fight any enemies who closed into the area so they wouldn't disrupt the sealing process for Team Three, who were going to seal the Three-Tails. After he had introduced himself to Shino, he found that Shino had a bit of a grudge towards Naruto, since it turned out that though Sai only knew Naruto for a few month and knew more about Naruto, much more than he did. Sai's team ran into Guren and Gozu. As the battle between them commenced, Sai soon took on Gozu alone. Sai managed to temporarily restrain him with his ink snakes but with his brute strength broke free shortly after. The sealing is disrupted and they were forced to retreat and devise another plan.

After he and the other Konoha-nin recuperated, he mistakenly got in between Sakura and Ino's bickering, and by being oblivious to the situation, repeated the names they yelled at each other thus getting himself punched by both of them. He and the others at some point find out that the young boy accompanying the enemies can partially control the beast. They eventually find him unconscious and take him with them. After Yūkimaru was treated by Sakura and Ino, Kakashi decided to use him to conjure up the beast to try sealing once more. After that Sai was tasked with bringing him to an secure place. However, he got attacked by some of Guren's men and despite his efforts, he was defeated and Yūkimaru was captured. Later, he battled foes who were merged but were crushed by the Three-Tails on its ramapage. Having failed to seal the beast again, they returned to their village and left the rest up to the leaf Anbu.

Itachi Pursuit Mission
Along with Team Kurenai, Sai and the rest of Team Kakashi set out to find and capture Itachi Uchiha. When Kakashi summoned his ninken to assist them on the mission, Sai was partnered with Ūhei and Urushi and wondered to himself whether or not he could become friends with dogs.

Fated Battle Between Brothers
He and the other members of the Eight Man Squad were later confronted by Tobi, who stalled them long enough to prevent them from locating neither Sasuke nor Itachi.

Six-Tails Unleashed
In the anime, Sai and the rest of Team Kakashi was assigned a mission involving the Tsuchigumo Clan. When they reached their destination they found the place a wreck and a hurt Tonbee. Sakura healed him and when he regained his strength, he told them that a group of ninja attacked, seeking the Tsuchigumo clan's kinjutsu, and that his granddaughter, Hotaru, escaped through a secret passage with it. Sai, Naruto and Yamato left to find her, leaving Sakura to look after Tonbee. When he, Yamato and Naruto caught up with her, they saw a mysterious guy named Utakata near her. Naruto attacked him under the impression he was a enemy to which it was clarified he was only escorting her until Konoha arrived. Utakata then left Hotaru in their hands, however, she was refused to it and Sai tricked her into letting them escort her to the Tsuchigumo Village. When the group reached the village they left her with the rest of her clan. They returned when they considered the villagers attitude toward Hotaru suspicious, and found she was gone.

Later, Sai and Naruto battled a few Kiri-Anbu because they were attacking Utakata who had Hotaru with him. The leader of the Kiri-nin took Yamato aside to discuss the matters of Utakata. After matters are solved to a certain degree, the groups departed. Sai and the rest soon find out that Hotaru had a scroll that held her clan's kinjutsu embedded in her back, much to the Konoha-nin's surprise.

Some time after, Team Kakashi and Utakata headed to the Tsuchigumo Village again after Hotaru had been kidnapped. While there, Sai, Yamato and Sakura fought the Tsuchigumo clan villagers who were under Shiranami's control and the Magaki Group while Naruto and Utakata went find Hotaru. They departed after Shiranami was defeated and his plan failed.

Pain's Assault
When Naruto entered the Hokage's office, he was seen with Sakura, the toads, Shizune and the Hokage as Naruto learned of his master's demise. During Pain's assault on Konoha, Sai was away with Yamato and Anko Mitarashi, tracking down Kabuto Yakushi. He used a special tracking technique that could not be detected by Kabuto. Anko even congratulated him for that. They stopped the search just after a surprised Yamato had informed the group that Naruto had reached the six-tailed form of the Nine-Tails.

Five Kage Summit
After the invasion, Danzō is made Hokage. He summoned Sai before him and instructed him to keep an eye on Naruto. Sai asked why, so Danzō explained that Naruto, having defeated Pain, was now the village's hero and thus more popular than Danzō himself. However, he was still the village's jinchūriki and therefore must be kept in check. Sai was satisfied with his explanation and went to meet with Naruto and Sakura. The two immediately confronted him about Danzō, asking him to tell them everything he knew. Sai said that he could not, as the cursed seal Danzō had placed on his tongue prevented him from revealing anything about Root. Sakura remarked it was cruel, but Sai explained that it was for the best since Root had done a number of questionable things to protect the village. Sakura refuted his claim, pointing out that Danzō had ordered Sasuke be killed as a traitor. Sai was surprised since Danzō had not told him that during their meeting. They were immediately confronted by Kumogakure ninja who, after their brief skirmish, demand to know what they knew about Sasuke. Naruto, seeing that this upset Sakura, volunteered to tell them all that he knew. Sai secretly watched the meeting and how Naruto could not bring himself to sell out Sasuke.

Naruto allowed Karui to take out her anger on him. Karui happily accepted and proceeded to beat him up, but Sai stepped in once she started to overdo it. When Karui left, Sai brought Naruto to Kakashi and Yamato and then tended to his wounds. Naruto asked that Kakashi and Yamato help him find the Fourth Raikage. When they had agreed, Kakashi told Sai not to tell Danzō what Naruto was doing. After hearing such a request Sai looked rather upset and asked Kakashi if he didn't trust him because he was from Root, but Kakashi answered that he believed in him because he was also a member of Team Kakashi. Hearing these words made Sai happy and drove him to act more resolutely. Sai later approached Sakura, telling her about what Naruto had gone through with Karui for her benefit. He surmised that Naruto deeply loved Sakura, and that trying to make her happy, such as by bringing Sasuke back to the village, caused him constant pain.

Following the Konoha 11's decision to eliminate Sasuke themselves to prevent a war, Sakura asked Sai to help her track down Naruto so that she could speak with him. They found him in the Land of Iron and Sakura confessed her love to Naruto, so now he didn't need to bother fulfilling his promise of retrieving Sasuke. When Naruto didn't believe her, Sakura left with her group. Because she didn't mention the decision to kill Sasuke and that he felt responsible for what she was about to do because of what he had told her back in Konoha, he left an ink clone behind to tell them what Sakura had not. The clone also added that Sakura was likely planning to kill Sasuke personally, and mentioned that Sakura was still in love with Sasuke and wanted to stop him from sinking any lower.

The ink clone helped Kakashi locate Sakura. The real Sai, meanwhile, stopped Sakura from knocking him out and her other escorts, having suspected that she would try to get rid of them so she could fight Sasuke alone. Sakura convinced Kiba and Lee that Sai was a traitor and they started to fight him, but this only made it easier for her to knock out all three. As the ink clone dispersed it warned Kakashi of Sakura's actions. Sai and the others were later woken following the meeting with Sasuke, and as they return to the village they were met by three Root members. They inquired about what had happened. Sai affirmed that the seal disappearing was proof that Danzō had died. He then encouraged them to speak with Kakashi whom he addressed as the "new Hokage" about Root's future.

Power
In the anime, Sai and the rest Team Kakashi were sent to investigate the attack at Tonika Village. Splitting up into two, he goes with Yamato. While on their investigation they run into police from Hachō Village. After hearing an explosion from a distance he and the others go to the location. When arriving he battled Kabuto at first but soon enough a reincarnated Deidara stepped in and his attention was drawn to him. After Kabuto retreated he and Yamato went to gather information on The Hole.

While there, he and Yamato soon battled Deidara and a snake clone of Hidan. Later with assistance from Kakashi and the other Konoha-nin, they discussed Kabuto's possible intentions. After, he joined his comrades in battling Kabuto's reincarnated shinobi. Later, they all returned to Konoha, with Kabuto's plan failed.

Fourth Shinobi World War: Confrontation
When the Fourth Shinobi World War began, Sai was placed in the Surprise Attack Division. He created birds with his Super Beast Imitating Drawing for his Division to head into battle. When they entered the enemy's territory and the rest of the division began making a base camp, Sai took to the air to provide back up in case they were attacked. When he later spotted several explosions near the camp, Sai rushed back, eliminating one enemy as he arrived. Despite having a broken neck, the target got back up, revealing himself to be a reincarnated Shin. Shin apologised to his brother for being forced to fight him, unable to control his own movements because of the technique he was reincarnated with and because he was also being manipulated by Sasori. Sai and Shin traded blows until the rest of ambush team could come to help. Hoheto Hyūga revealed that there was explosive clay stored within Shin. They navigated him into one of Kankurō's puppets before he could detonate, weakening the explosion.

However, the force was still great enough to knock Sai over, causing some of the belongings from his bag to fall out. Shin regenerated from the damage and Deidara promised to use Shin as a human bomb again and again. Enraged, Sai quickly navigated behind Deidara and Sasori and drew two ink warriors that knocked them both into two more of Kankurō's puppets, where they were confined and neutralised. Sai then prepared to fight Shin again, but Shin told him there was no need; Sai had dropped his picture book earlier, and seeing the finished product had unbound his soul, freeing him of the regrets that he had had in life. Tears flowed from Sai's eyes as Shin's body turns to ash and dust.

Sai, Omoi, and Zaji were sent out to find other Akatsuki cells. When they came across a group consisting of Haku, Zabuza, Gari, and Pakura, Sai created several ink birds with explosive tags attached to bombard them with. Although the revived ninja recovered from their injuries, Sai continued the assault until backup could arrive. Haku managed to destroy the birds they were riding on, causing them to fall to the ground. Before they could be killed, fortunately, the Third Division arrived to help. They later joined the division in protecting Kakashi as he executed his strategy. After Zabuza and Haku had been dealt with, Kakashi asked that Sai back him up with the sealing techniques he had learned from Root. Sai was reluctant, but Kakashi insisted that, as one of Danzō's most prized soldiers, Sai needn't hold his emotions. Later, Sai was seen among the rest of the Third Division as they recuperated after the first day of war.

Fourth Shinobi World War: Climax
The next morning, Sai alongside the Third Division restarted their assault on the Seven Ninja Swordsmen of the Mist. Drawing a gigantic tiger, Sai launched his Sealing Technique: Tiger Vision Staring Bullet at Fuguki Suikazan who had been incapacitated by Kakashi. As the tiger dragged Fuguki back into the drawing, a noticeably winded Sai told them that he could still go on. Lee told Sai to just concentrate on sealing the enemies, he would protect him while Sai's at it. As a new wave of White Zetsu Army clones approached, Sai looked on as Naruto's shadow clone arrived on the battlefield to confront them. In the anime, Sai also used this technique to seal away Jinin Akebino, and a number of other reincarnated shinobi as well. After being informed by Inoichi from HQ that Naruto and B were fighting the "masked Madara", Sai and the Konoha 11 rushed to his aid. As he ran, he stated that if it were not raining, he could use his Super Beast Imitating Drawing technique to get to Naruto faster. After Lee had, however, spurred him on, Sai thought to himself that he finally and completely understood what it meant to have friends.

Upon arriving at the battlefield, he apologised to Kakashi for their late arrival and later stood alongside the remaining members of the Allied Shinobi Forces to face their opposition. When B had regained enough chakra, Sai flew him towards the Ten-Tails atop one of his birds, allowing B to get close enough to launch a counter measure against the beast.

Later as the Ten-Tails matured and the Alliance launched a counter assault, Sai attempted to attack the Ten-Tails' body from above, avoiding its copies, but was soon spotted and knocked out of the sky. After being saved by Naruto, Sai concluded the only way to reach the beast was to take out the larger enemies first and slither past, but that would require a method to get into range quickly and once they were there they would be without healers. His team-mates of Team Kakashi responded by summoning a snake, a toad, and a slug respectively.

While the Allied Shinobi Forces and the deceased Hokage marvelled at the original Team 7's combined performance, Sai questioned Jūgo about Sasuke's true motives, to which he replied that even he himself didn't know. He would later tell Sakura that since he didn't know Sasuke much he could observe him without friendly feelings involved and that he couldn't trust him. He proceeded to question Sakura how she truly felt about Sasuke, to which she replied that she was happy Sasuke had returned and that they could trust him. Sai then thought that sincere as her words sounded, her smile was fake.

Birth of the Ten-Tails' Jinchūriki
After the Ten-Tails transforms into its true, tree-like form, it ravaged the Alliance in an attempt to consume their chakra. Sai, seemingly having avoided the assault, crouched and tended to a wounded Sakura. Thankful that Sakura was all right, their attention is soon drawn to Shikamaru's predicament. When Katsuyu noted that it would not be able to remotely assist him because its clones had been killed as well, Sai and Sakura rushed to Shikamaru's side to help their fallen comrade. Responding when Naruto called for them telepathically, Sai the Konoha 11 shinobi are shocked when Naruto's Tailed Beast Mode mantle forms around them as well when he enters one of Kurama's tails. His directives clear, Sai and the others used the Rasengan, which Naruto had formed to break down Obito's defence and give Sasuke and Naruto a clear shot at attacking their opponent. He and his comrades later also aided Naruto in wresting control of the tailed beasts' chakra from Obito in order to stop the Ten-Tails' tree form from blooming. Ultimately, they succeed in removing the tailed beasts from Obito, reverting the Uchiha to his original form. Sai then joins the others in aiding Hashirama against Madara.

After Hashirama is able to subdue the Uchiha, Sai moves in to seal him for good. Moments before the seal is complete, Madara has Black Zetsu merge with Obito, forcing him to revive Madara, granting Madara full access to his newfound might and break free of both Sai's seal and Hashirama's restraints. After being revived and gaining access to his full power, though without his dōjutsu, Madara was easily able to overwhelm the shinobi in the surrounding area, including Sai, before absorbing Hashirama's senjutsu chakra and going to capture the nine tailed beasts. Sai then teamed up with Sasuke, letting the Uchiha perform a sneak attack from the air through the use of a ink bird.

Much later, after Madara became the Ten-Tails' jinchūriki and reclaimed his missing eye, Sai stood next to Hashirama while the Infinite Tsukuyomi was cast, before falling prey to it like the rest of the world and being captured by the roots of the Ten-Tails.

Kaguya Ōtsutsuki Strikes
Ultimately, Sai was freed from the genjutsu by Naruto and Sasuke as the war finally ended.

Kakashi Hiden: Lightning in the Icy Sky
Nearly a year after the end of the Fourth Shinobi World War, Sai and Naruto are on a mission in the Land of Waves to capture Garyō, leader of the Ryūha Armament Alliance, a group that follow the example set by Madara Uchiha, and in doing so has cost the lives of several of the Land of Waves' citizens. While dealing easily with most of the enemy forces, Garyō's bodyguard holds them off using Ice Release. Garyō insists that his group is doing the world some good by releasing it from the corruptive influence of money. Ultimately, Sai and Naruto capture Garyō on and leave on Sai's bird.

Two months later, when the Tobishachimaru, an airborne ship, is commandeered by Garyō's men in an attempt to free him from the Hōzuki Castle, Sai is sent to aid Kakashi in the air. Sai arrives in to save Kakashi and Guy as they begin falling from the sky. Kakashi informs Sai of what they learned about the Armament Alliance's shinobi and asks how things are going on Konoha's end. Kakashi sends a message to Ino that Tobishachimaru is heading to Blood Prison and asks Sai to take him back to the ship so he can try and stop it. Sai complies, but finds the Tobishachimaru has risen well above its usual altitude owing to the ongoing conflict on board. After getting Kakashi back inside, the hijackers agree to let Sai take a young boy with asthma off the ship but is warned they will kill a hostage if they see him again.

Shikamaru Hiden: A Cloud Drifting in Silent Darkness
Sai makes an appearance in this novel.

The Last: Naruto the Movie
Two years after the Fourth Shinobi World War, Sai was drawing a scenery outside of Konohagakure in the middle of the night, only to notice the moon's descent towards the Earth and a hooded shinobi riding on a flying creature while carrying the unconscious Hanabi Hyūga, much to his shock. He tried to chase after them, only to be taken down before he could rescue Hanabi. After reporting to the Sixth Hokage about Hanabi being kidnapped by Toneri Ōtsutsuki, he joins with Naruto, Sakura, Shikamaru, and Hinata on a mission to rescue her.

After Naruto is brought out of his depression by Sakura, she and Sai go to save Hanabi while Naruto and Shikamaru go after Hinata. After Toneri's defeat, the group heads back for Konoha. Later, as Naruto began dating Hinata, he borrowed one of Sai's instruction books about relationships, particularly about dating protocol.

Later, Sai was seen at Naruto and Hinata's wedding. He was also seen holding Ino's hand, hinting they were in a relationship at the time.

Sakura Hiden: Thoughts of Love, Riding Upon a Spring Breeze
Sai makes an appearance in this novel.

Epilogue
Years later, Sai eventually married Ino, and the two had a son named Inojin, whom Sai helps train to become part of the new generation Ino–Shika–Chō, with assistance from his wife.

Naruto Gaiden: The Seventh Hokage and the Scarlet Spring
Sai began teaching his son his art-based ninjutsu, with Inojin noting that his father's art is ancient.

Naruto Shippūden the Movie: Bonds
Sai, due to his ability to create flying mounts for himself with his Super Beast Imitating Drawing Technique, served a double function as a scout and first counterstrike against the Land of the Sky attackers by using taijutsu to jump and wreck different the Land of the Sky shinobi wing sets. He admits, soon after, that he is actually bored with the incompetence of the Sky ninja.

Naruto Shippūden the Movie: The Will of Fire
After being sent to scout the area, Sai is knocked out of the sky and is later found unconscious by Naruto. Although not officially given a mission, after recovering from previous injuries, Sai pursued the Konoha 11 on their way to Hiruko's base. Temporarily blinding San with a flashbomb, he picked up Naruto and Sakura in order to get them ahead of the following teams, leaving Shikamaru and his team-mates to deal with San.

Naruto Shippūden the Movie: The Lost Tower
When Naruto and Yamato are taken into the seal Mukade broke, Sai saves Sakura from being pulled into it as well. When Naruto and Yamato reappear, they all go back to Konoha.

Road to Ninja: Naruto the Movie
The alternate world's Sai, compared to the Sai that Naruto and Sakura know, has more emotions within himself and is more outgoing. His passion for art is the same, the only difference is that his alternate self is horrible at it. Also, due to the alternate Sasuke still being part of Team 7, the alternate Sai never became a member of Team 7 nor does he know the others.

Trivia

 * As an Anbu member, Sai refers to Kakashi as his senpai out of respect.
 * Between the end of the Fourth Shinobi World War and the events of The Last: Naruto the Movie, Sai changes his rank from "Anbu" to . Currently, it is not known what exactly this change implies.
 * According to the databook(s):
 * Sai's hobbies are drawing and calligraphy.
 * Sai wishes to fight Kakashi Hatake.
 * Sai's favourite word is.
 * Sai's favourite food is momen tofu, while his least favourite is mitarashi dango.
 * Sai has a frank, obedient and submissive personality.
 * In the seventh character poll, Sai placed 12th place, alongside Sakura, with 2,188 votes each.
 * Sai's fake smile and mannerisms greatly resembles Seta Sōjirō from Rurouni Kenshin anime series.

Quotes

 * (To Naruto) "The way you fight, are you a boy or a girl?"
 * (To Sakura) "A smile can get you out of a tough situation, even if it is fake."
 * (To Sakura) "I've drawn hundreds, maybe thousands of pictures so far… other pictures have the situation at the time, and the artist's feelings… like portraits have the person's name… but don't pictures usually have titles…? To be more precise, even if I try to give them titles, I just can't do it. I don't feel anything… they don't put me in mind of anything."
 * (To Sakura) "…I don't have any of what you'd call "emotions"."
 * (To Sasuke) "Even when I force myself to smile. It seems I'm the type of person who ends up being hated."
 * (About Sasuke) "…yet by just looking into his eyes, does this mean I fear Sasuke deep within my heart, despite being unable to recognise it myself…?"
 * (To his team) "Sai is the name I was given for this mission… I'm nobody. I am a tool for Lord Danzō. I don't exist."
 * (To his team about his adoptive brother) "We weren't connected by blood, but he did compliment me on my drawings quite a bit."
 * (To his team about the picture book) "The centre of two pages were the ones I wanted to show my brother the most, but since he's dead, I can't remember what I wanted to draw on them."
 * (To Kabuto) "If people change… then so can I. But some things never change. Bonds. I'd like to learn more about them."
 * (After finishing the picture book) "This is what I wanted to show my brother. The picture of our dreams."
 * (To Sakura) "Lately when I look at Naruto I've been able to feel it… his sadness. And when he thinks of Sasuke there's a heat coming from his gut and I know that's anger. For Naruto's sake, for Konoha's sake, we need to do something ourselves instead of always relying on him."
 * (To himself) "This… is what it means to have friends… I understand it perfectly… Naruto."