Sai

is an ANBU-level shinobi from the disbanded faction: Root who later became one of the main supporting characters of the series. He is also a member of Team Kakashi, having replaced Sasuke Uchiha.

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. But after bonding with Naruto Uzumaki, Sai remembers and completes the book, causing him to give his first genuine display of emotion in a long time: a smile.

Before his appointment to Team 7, Sai — under Root's orders — had been eliminating individuals that worked 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 tended to get people angry, because he would often speak 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". Luckily Naruto covered his mouth before he could finish.

After spending more time with Team Kakashi, Sai comes to appreciate bonds, particularly the bond that exists between Naruto Uzumaki and Sasuke Uchiha. This causes him to break out of his emotionless shell and he starts 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. 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 becomes enraged and attacks Sasori and Deidara mercilessly, showing genuine rage on his face. Sai also displays genuine sadness, shedding tears when his brother is 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 burden. What he failed to understand, however, was that Naruto was not trying to save Sasuke just for Sakura. Naruto simply wanted to save his friend, something he would later regret and try to make amends for after understanding how by telling Sakura his misinterpreted view of Naruto's pain it had ultimately put her in grave danger. Sai holds Naruto in high regard, and tries to assist Naruto whenever he's going through hardships.

Appearance
Sai has short, black hair, black eyes which contrasts with his very pale skin. He is usually seen carrying a small backpack with his brush, scrolls, and ninja ink in it. He wears a short black 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 shirt had a long right sleeve and a short left sleeve. 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 black is apparently ink, as when Danzō countered the symptoms, ink splattered from Sai's body.

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. As an ANBU, Sai also uses a tantō.

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.

According to 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 whith his tantō. He also was able to subdue Kabuto Yakushi very easily and block Sasuke Uchiha's attempt to stab Naruto, Sasuke even 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. He is also very proficient with the Body Flicker Technique, and is capable of surprising even highly-skilled shinobi with it.

Sasuke and Sai Arc
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 is confrontational with his new team-mates, questioning Naruto's manhood and insulting Sasuke. The latter causes Sakura Haruno to punch him in anger. As they continue on to the meeting point, Sai questions why Naruto is loyal to a traitor like Sasuke, to which Naruto said he's 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 begin fighting, Sai leaves the rest of the team to begin his real mission. He observed Naruto's fight with Orochimaru, unconcerned with the danger he left Yamato and Sakura in, and approaches Orochimaru after he had repelled Naruto with a proposition from Danzō. Orochimaru accepted, and Sai accompanied him and Kabuto back to their hideout.

Once arriving 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 with Naruto, Sasuke fixed him with a stare, startling Sai due to the amount of fear it gave to 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. 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 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 to capture 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 are soon found by Orochimaru, and Naruto distracts him so that Sai can have a chance to scout on ahead. When Orochimaru retreats and Naruto reunites with Sakura and Yamato, Yamato goes through the belongings that Sai left behind. In doing so he discovers Sai's actual mission: to kill Sasuke as a traitor to Konoha. Team Kakashi races through the base to find and stop Sai, but Sai has already found Sasuke. Sai, however, truly had a change of heart, and tries to capture Sasuke in order to protect his bond with Naruto.

Irritated by Sai's reasons for bothering him, Sasuke attacks Sai, drawing the rest of the team to their location. When they find out what Sai was trying to do, they all team up to restrain Sasuke. Although Sai is able to land a successful attack, Sasuke's abilities are too much for them and he prepares to kill them all. He is stopped by Orochimaru and Kabuto, who convince him to spare the team before leaving. Defeated, Team Kakashi returns home. Sai requests that he be allowed to stay a part of the team and, with Danzō's approval, begins spending time with his new friends.

At one point, Sai begins visiting the Konoha library to read about relationships in the hopes of making some for himself. In the anime, this begins before and continues throughout the Twelve Guardian Ninja Arc. When he reads that nicknames are a good way to make friends, Sai makes the mistake of using nicknames that describe how he actually sees a person. When calling Sakura "ugly" earns him a beating, he concludes that women like to be called the opposite of what is true. To that end, he calls Ino Yamanaka "beautiful", something that receives another beating from Sakura.

Hidan and Kakuzu Arc
Sai and the rest of the team are later sent to provide 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 as backup for him, 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 get back. Sai, to improve their friendship, feeds Naruto, angering Naruto because he had wanted Sakura to feed him. Neither has their way when Kakashi arrives to feed Naruto instead.

Itachi Pursuit Arc
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 is partnered with Ūhei and Urushi and wonders to himself whether or not he could become friends with dogs. He and the others are later confronted by Tobi, who stalled them long enough to prevent them from locating neither Sasuke nor Itachi.

Invasion of Pain Arc
When Naruto entered the Hokage's office, he is seen with Sakura, the toads, Shizune and the Hokage when Naruto learnt of his master's demise. During the invasion of Pain, Sai is away with Yamato and Anko Mitarashi, tracking down Kabuto Yakushi. He used a special tracking technique that can not be detected by Kabuto. Anko even congratulated him for that. They stopped the search just after a surprised Yamato tells the group that Naruto has reached the six-tailed form of the Nine-Tails.

Five Kage Summit Arc
After the invasion, Danzō is made Hokage. He summons Sai before him and instructs him to keep an eye on Naruto. Sai asks why, so Danzō explains that Naruto, having defeated Pain, is the village's hero and thus more popular than Danzō himself. However, he is still the village's jinchūriki and must be kept in check. Sai is satisfied and goes to meet with Naruto and Sakura. The two immediately confront him about Danzō, asking that he tell them everything he knows. Sai says that he cannot, as the cursed seal Danzō placed on his tongue prevents him from revealing anything about Root. Sakura says it is cruel, but Sai explains that it is for the best since Root has done a number of questionable things to protect the village.

Sakura refutes his claim, pointing out that Danzō has ordered Sasuke be killed as a traitor. Sai is surprised, Danzō not having told him that during their meeting. They are immediately confronted by Kumogakure ninja who after their brief skirmish ask for what they know about Sasuke. Naruto, seeing that this upsets Sakura, volunteers to tell them all that he knows. Sai secretly watches the meeting and how Naruto cannot bring himself to sell out Sasuke.

Naruto allows Karui to take out her anger on him. Karui happily accepts and begins beating him up, but Sai steps in once she starts to overdo it. When Karui leaves, Sai brings Naruto to Kakashi and Yamato and then tends to his wounds. Naruto asks that Kakashi and Yamato help him find the Fourth Raikage. When they agree, Kakashi tells Sai not to tell Danzō what Naruto is doing. After hearing such a request Sai looks rather upset and asks Kakashi if he doesn't trust him because he is from Root, but Kakashi answers that he believes in him because he is also a member of Team Kakashi. Hearing these words makes Sai happy and drives him to act more resolutely. Sai later approaches Sakura, telling her about what Naruto went through with Karui for her benefit. He surmises that Naruto loves Sakura, and that trying to make her happy, such as bringing Sasuke back to the village, causes him constant pain.

Following the Konoha 11's decision to eliminate Sasuke themselves to prevent a war, Sakura asks that Sai help her track down Naruto so that she can speak with him. They find him in the Land of Iron and Sakura tells Naruto that she loves him, so now he doesn't need to bother fulfilling his promise of retrieving Sasuke. When Naruto claims she is lying she leaves. Because she doesn't mention the decision to kill Sasuke and that he feels responsible for what she was about to do because of what he told her back in Konoha, he leaves an ink clone behind to tell them what Sakura did not. The clone also adds that Sakura is likely planning to kill Sasuke personally, and mentions that Sakura is still in love with Sasuke and wants to stop him from sinking any lower.

The ink clone helps Kakashi locate Sakura. The real Sai, meanwhile, stops 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 convinces Kiba and Lee that Sai is a traitor and they start to fight him, but this only makes it easier for her to knock out all three. As the ink clone disperses it warns Kakashi of Sakura's actions. Sai and the others are later woken following the meeting with Sasuke, and as they return to the village they are met by three Root members. They inquire about what has happened. Sai affirms that the seal disappearing is proof that Danzō has died. He then encourages them to speak with Kakashi who he addressed as the "new Hokage" about Root's future.

Chikara Arc
In the anime, Team Kakashi is tasked to investigate the Tonika Village, which was just recently wiped out by unknown aggressors. Seing the aftermaths of the massacre, Sai accompanies Yamato to search through the village until they are found by local troops from the neighbouring village. After being informed about the incident, they notice that Naruto and Sakura started a fight with Kabuto Yakushi. Sai is shocked by the sight of the reincarnated Akatsuki members and attackes Kabuto. He is however intercepted by Deidara and is forced to fight him instead.

Shinobi World War Arc
When the Fourth Shinobi World War begins, Sai is placed in the Surprise Attack Division. He creates birds with his Super Beast Imitating Drawing for his Division to head into battle. When they enter enemy territory and the rest of the division begins making a base camp, Sai takes to the air to provide back up in case they are attacked. When he later sees several explosions near the camp, Sai rushes back, eliminating one enemy as he arrives. Despite having a broken neck, the target gets back up, revealing himself to be a reincarnated Shin. Shin apologises 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 trade blows until the rest of ambush team can come to help. Hoheto Hyūga reveals that there is explosive clay stored within Shin. They navigate him into one of Kankurō's puppets before he can detonate, weakening the explosion.

However, the force is still great enough to knock Sai over and release some of his belongings from his bag. Shin regenerates from the damage and Deidara promises to use Shin as a human bomb again and again. Enraged, Sai quickly navigates behind Deidara and Sasori draws two ink warriors that knocks both into two more of Kankurō's puppet, where they are confined and neutralised. Sai then prepares to fight Shin again, but Shin tells him there is 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 in life. Tears flow from Sai's eyes as Shin's body turns to ash and dust.

Sai, Omoi, and Zaji are sent out to find other Akatsuki cells. When they come across a group consisting of Haku, Zabuza, Gari, and Pakura, Sai creates several ink birds with explosive tags attached to bombard them with. Although the revived ninja recover from their injuries, Sai continues the assault until backup can arrive. Haku manages to destroy the birds they are riding, causing them to fall to the ground. Before they can be killed the Third Division arrives to help. They later join the division protecting Kakashi while he executed his strategy.

After Zabuza and Haku are dealt with, Kakashi asks that Sai back him up with the sealing techniques he learned from Root. Sai is reluctant, but Kakashi insists that, as one of Danzō's most prized soldiers, Sai doesn't need to hold his emotions. Later, Sai is seen among with the rest of the Third Division as they recuperate after the first day of war.

The next morning, Sai alongside the Third Division restart their assault on the Seven Ninja Swordsmen of the Mist. Drawing a gigantic tiger, Sai launches his Sealing Technique: Tiger Vision Staring Bullet at Fuguki Suikazan who had been incapacitated by Kakashi. As the tiger drags Fuguki back into the drawing, Sai noticeably winded tells them that he can still go on. Lee tells Sai to just concentrate on sealing the enemies, he would protect him. As a new wave of White Zetsu Army clones approach, Sai looks on as Naruto's shadow clone arrives on the battlefield to confront them.

After being informed by Inoichi from HQ that Naruto and B were fighting the "masked Madara", Sai and the Konoha 11 rush to his aid. As he runs, he states that if it weren't raining he could use his Super Beast Imitating Drawing technique to get to Naruto faster. After Lee spurs him on, he thinks to himself that he finally and completely understood what it meant to have friends.

Naruto Shippūden 2: 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 Sora-nin attackers by using taijutsu to jump and wreck different Sora-nin wing sets. He admits, soon after, that he is actually bored with the incompetence of the Sora-nin.

Naruto Shippūden 3: Inheritors of the Will of Fire
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 flashbang, 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 4: 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.

Naruto 6: Road to Ninja
The alternate world's Sai, compared to the Sai that Naruto and Sakura know, has more emotions with himself and more outgoing. His love for art is the same, only 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.
 * 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 Naruto Shippūden opening, Sai is shown fighting Asura Path, though in the manga, they do not fight; in fact, he isn't even present in Konoha when Nagato and Konan attacked.
 * In the seventh character poll, Sai placed 12th place, alongside Sakura, with 2,188 votes each.

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."
 * "…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."