Sai

is a young ninja from the Foundation who specializes in techniques that use ink. He replaces Sasuke in Team Kakashi.

Background
One of many nameless orphans recruited into Konoha's secret branch, Foundation, Sai was raised and conditioned to have no personality or personal connections. The name "Sai" is given to him for the purposes of joining Team 7. His actual name is currently unknown, even to himself. Sai was recruited as the newest member of Team Kakashi by Danzo, the commander of the Foundation, to join Naruto Uzumaki and Sakura Haruno as a replacement for Sasuke Uchiha after his defection from Konoha.

During his time among the Foundation, Sai met Shin, an older member of the same organization who took a liking to Sai's drawing ability. Over time, Sai came to think of Shin as an older brother and looked up to him. Eventually, his "brother" died of an unnamed illness, and Sai's Foundation training suppressed most of the memories he had for his brother. Before Shin's death, Sai was making a picture book that would depict all the opponents that they faced and illustrate the feelings that they shared for each other. Sai's and Shin's portraits are located at opposite ends of the book, and in the center pages would be a picture of both him and his brother holding hands. Shin died before Sai could complete the book, but on their mission to save Sasuke, Sai noticed that Naruto's face reminded him of Shin, and so while they were there Sai finished the picture. After finishing the picture, Sai showed the first sign of emotion by smiling.

Personality
When first introduced, Sai was distinguished by total lack of emotion which he often masks with a false, cheerful, yet transparent facade. After much mental conditioning and training while in Foundation, 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, both his own lack of social experience and personal initiative cause for Sai to have great trouble in understanding how bonds and friendships between people can motivate others. He often showcases this confusion after thinking about why Naruto would go so far to save Sasuke, even though Naruto had not been ordered to do so.

Sai is also very observant, and is always focused on his missions. He pays much attention to detail, allowing him to notice if something is not as it appears or should be, as shown from how he easily sees through Yamato's tricks.

Sai is also a talented artist, but his lack of feelings prevents him from ever titling his work. His lack of social skills and obviously false outer mask frequently causes conflict between Sai and Team Kakashi, and he often makes the mistake of insulting the other members in an attempt to seem sociable. He tries to seem more compassionate by smiling, though his teammates come to dislike it due to his obvious insincerity.

After spending more time with his team, Sai comes to appreciate bonds, particularly the bond that exists between Naruto Uzumaki and Sasuke Uchiha. After spending more time with Team Kakashi, Sai eventually begins to break out of his emotionless shell and starts to remember the times he had with his own "brother." 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 his own, more pleasant, and thoughtful personality, while 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.

Living Art
Sai's most notable talent is his skill as an artist, and he has claimed to have drawn thousands of pictures. Despite the great quantity and magnitude of the things he has drawn, he has never given one 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 ability is also the source of his jutsu, known as Super Beasts Imitation Picture. By drawing objects with a brush on his scroll he is able to bring his creations to life by animating the ink directly off the page. Similar to Deidara's clay-based jutsu, Sai's ink-based jutsu increases their size and allows his art to move and attack opponents at a distance. Of his seen creations, he uses giant birds for long range transport, lion-like monsters for attack, small rats for scouting and numerous small serpents to capture targets. The jutsu requires actual pictures to be drawn on the scroll before coming to life, and Sai has been shown as capable of drawing these sketches at alarmingly fast speeds. Likewise, by creating an of himself, he can perform a reconnaissance of an area without actually endangering himself. Sai can also transform words he writes on his scroll into small animals that seek out their target and revert back to words upon arrival, giving Sai a way to communicate easily over long distances. Also, as seen when he fought Naruto, he appears to be able to transport himself across short distances by surrounding himself in ink and making the same hand seal that he uses in his Super Beast Imitation Picture. Sai has also shown the ability to make items out of ink, like when he made an umbrella for Sakura to stay dry under.

Other Fighting Skills
In addition to his art-based ninjutsu, Sai has also shown himself to be a capable fighter, being able to effectively counter and perform attacks, such as when he blocked Sasuke's attempted kill on Naruto and when he subdued Kabuto.

Sasuke and Sai arc
Sai was assigned to join Team Kakashi by his superior Danzo, and first introduced himself to Naruto by attacking him when Naruto was meeting Shikamaru and Choji again. The fight culminated in Sai disappearing the same way that most Jonin do, but using ink instead of smoke. After later meeting Sakura and temporary Team Kakashi leader Yamato, the group set out to meet a spy of Sasori who had infiltrated Orochimaru's ranks. Soon after leaving Konoha, Sai began to bad-mouth Sasuke Uchiha, earning him a punch from Sakura. Sai's standing with the team didn't improve as their trip continued, as he often insulted Naruto's manhood. When Naruto defended Sasuke, Sai wondered why someone would protect a "traitor" to which Naruto said he's not a traitor, but a friend. This concept was lost to Sai, who seemed to have no friends, and when asked if he even knew what friend meant, he showed a scroll with the word written on it.

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. Soon after, Naruto and Orochimaru did battle, signaling the start of Sai's real mission. After leaving Yamato's side and deciding not to to save Sakura from falling off of a cliff, Sai watched Naruto and Orochimaru's fight from the cover of the neighboring trees. When Orochimaru eventually repelled Naruto, Sai approached him with a proposition from Danzo. Orochimaru accepted, and Sai accompanied him and Kabuto back to their hideout.

Along the way, Kabuto created a Sai lookalike and left it behind to throw off anyone who may be following them. 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. Sasuke seemed indifferent to him, expressing discontent towards Orochimaru instead. 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.

After his meeting with Sasuke, Sai was lead to his own room by Kabuto, who locked Sai in when he left. Soon after arriving in the room, Team 7, having put extra precautions into following Sai, arrived and confronted Sai about his defection to Orochimaru. Because he had been caught, Sai divulged the information about his true mission: to ally with Orochimaru on Danzo's behalf so that the two may join forces in destroying Konohagakure. Disgusted by the ramifications of this plan, Team 7 took Sai from Orochimaru's lair and restrained him. With Sai out of the way, Team 7 prepared to go looking for Sasuke, hoping to bring him back to Konoha. 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.

Just as Team 7 was about to leave Sai, Kabuto arrived and released him, hoping that the two would be able to defeat Naruto, Sakura, and Yamato easier as a team. Before any fighting can begin, however, Sai, moved by Naruto's words and hoping to understand the concept of "bonds" better, helped Yamato immobilize Kabuto. After extracting some information from Kabuto, Naruto and Sai broke away from the rest of Team 7 to find Sasuke. While they rest, Sai remarked how Naruto reminded him of his older brother, bringing an actual smile to his face as a result of his brother's memory.

Sai's happiness was short-lived, as Orochimaru soon arrived in an attempt to see where Sai's loyalties really lie. With Naruto's encouragement, Sai left the scene with the assignment to find Sasuke. As Sai searched the numerous rooms of Orochimaru's lair, Naruto was rejoined by Sakura and Yamato, forcing Orochimaru to retreat. As Yamato went through the belongings that Sai left behind, he found a Bingo Book that had Sasuke listed as a target, indicating that Sai's actual mission has, from the very start, been to kill Sasuke.

As Team 7 split up again to catch Sai and stop him from accomplishing his mission, Sai finally found Sasuke asleep in his room. Sasuke, however, was quick to notice Sai's presence and asked what he wanted. Sai responded by saying that he was going to bring Sasuke back to Naruto instead of carrying out his mission, willing to fight to protect the bond that Naruto would give his life to defend. Angered that Sai woke him up for a discussion about bonds, Sasuke attacked Sai, destroying the room and caused a large crater to be left in its place. Team 7, attracted to the scene of the attack, confronted Sai about his actual motives. Upon learning of what Sai was trying to do, Sai was welcomed back into the ranks of Team 7, and the group joined together in an attempt to defeat Sasuke.

As the group surrounded and attacked Sasuke, Sai's attack was the only one that manages to be effective. After Sai was congratulated by Sasuke for this feat, the latter used his Chidori Current to throw the group back. Uninterested in having a drawn out fight, Sasuke prepared to finish the group with a single attack, Kirin, though before he could do so Orochimaru and a freed Kabuto arrive to stop him, and the three disappeared. Team 7, having failed their mission, returned to Konoha. After, however, Sai drew a picture of him and Team 7, with the scroll he had shown earlier next to it with the word "Friends."

As Team 7 recuperated, Sai used his spare time to read up on relationship skills and gaining people's trust at the Konoha library. As one could expect from someone who learned to communicate with others via a book, Sai initially had problems putting what he read into practice, but Naruto told him not to worry about being formal. Sakura tried to help with nicknames by calling Naruto stupid as an example. Sai then thanks Sakura and calls her Ugly dog as her nickname, this earns him a punch... During Team 7's dinner with the members of Team 10, Sai puts what he learned into practice, though found little success, he almost called Choji fatso and calls Ino Ms beautiful, thinking that if he dosen't say the opposite of what he thinks with girls, he'll get another punch. However Sakura gets even more pissed off because of this, and yet again, another punch!

Fire Temple arc
Still being a part of Team Kakashi, Sai was ordered to join his new teammates in a mission to the Fire Temple. While camping out with his team while waiting for their guide from the temple, Sai mistook Naruto's anxiety for wanting to continue his training as being afraid of the dark. While trying to help Naruto calm down, he instead ended up making Naruto very uncomfortable and causing him to storm off in anger.

Later after arriving at the Fire Temple and learning about one of the Twelve Ninja Guardian corpses being stolen, he joined his team and members of the Fire Temple in retrieving three more stolen Ninja Guardian corpses. They follow a trail to a grassy field, only to be ensnared in the enemies' trap; causing the entire terrain to transform into a rocky canyon. After being seperated by from his team, one of the tomb robbers, Fuen, plants a tracker on Sai and begins targeting him with several traps. Eventually, Sai discovers the tracker and places it on an Ink Clone to deceive Fuen. While failing to defeat Fuen, he managed to shake her long enough to go in search of his teammates.

He later finds Sakura in time to save her from being attacked by a giant spider. Unfortunately, in the process Sai sustained a broken arm. While Sakura was able to heal the major damage, he was still required to be put out of action temporarily. Despite his injured status, Sai still proved to be of use. While Asuma was having difficulty battling against Kazuma's new arsenal of techniques, Sai snuck up on Kazuma with one of his ink snakes and restrained him. After everyone managed to save Sora from his demon chakra and was told he had friends, Sai shyly asked if he could be his friend too.

Hidan and Kakuzu arc
While Naruto continues his training to complete the Rasengan, Sai watches with great interest, wondering if Naruto really can succeed where ninja with the skill and might of the Fourth Hokage, Jiraiya, and Kakashi failed. Despite his own uncertainty, he used what he learned from books to give Sakura more faith in Naruto. Sai later came to Team 10's aid in their fight against Akatsuki members Hidan and Kakuzu. 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.

After returning home, Naruto, Sai, and Sakura went to eat ramen. Naruto had trouble eating his food because his right hand was broken, so Sai ended up interrupting a tender moment between Naruto and Sakura by stuffing Naruto's face with noodles because he read in a textbook that he should help his friends. While this is usually true, Naruto went off on him for ruining the moment. In the end though, Kakashi ended up feeding Naruto. (Coincidentally, he heard all of the commotion and came in to see what was wrong.)

Three-Tails Arrival arc
When Tsunade learns of a dangerous new opponent faced against Team 8, Tsunade orders Team Yamato to go as backup, which still included Sai. Before leaving, Sai went to a store to stock up on his special ink. He was then confronted by Naruto, who suspected he was going on a mission. Sai tried to fool him with what he learned from (yet another) book, but Naruto was ultimately able to make Sai reveal the truth, much to his shame.

Later when finding it hard to locate Team 8, Sai is sent out with his art jutsu to search the area from the sky. He ultimately finds that much of the forest has been encased in crystal. As Naruto offers a solution, Sai watches in amazement that Naruto can not only perform the Summoning Technique with toads, but is also able to perform yet another high level jutsu of synchronizing with his summoning to blast down the crystal.

Sai and his team then finds Team 8 up against Guren. Sai then performs the main part of a distraction to aid his team in rescuing Hinata. After freeing Hinata, the team once again goes in search of the enemies.

Upon finding their enemies, they soon discover that an even greater danger has made an appearance. That said presence then launches a huge tidal wave at Sai and his allies. After Sai and his allies escape the wave, a powerful fog appears. Sai then flies with Hinata high into the sky on his ink bird to allow her to look at the area with her Byakugan better.

After learning of the Three-Tailed Beast's arrival, Sai is put on a primary defense team to stop intruders from stopping the Three-Tails sealing. Along the way, he is intrigued to meet more of Naruto's friends and allies and shows detailed knowledge of their background. When Guren and Gozu finally appear, Sai faces off against Gozu, managing to initially subdue his opponent until he transforms into mud.

After Guren escaped from battle, Sai began using his ink animals to survey the area to further protect the seal on the Three-Tails. After the Three-Tails escapes, Sai and the others instead find Yukimaru, who they take back to their hideout.

After learning that Naruto was swallowed whole by the Three-Tails along with Guren, Sai was assigned sky surveilence. He was also given a task of gather as many camelias as possible for Yukimaru to aid in the rescue. After doing so, Sai was ordered to take Yukimaru away for safety. Unfortunately, he was attacked by the enemies again and incipaciated, but not before sending another message to Kakashi through one of his ink creatures.

After recovering, he joins his team in directly protecting the sealing team.

Hunt for Uchiha arc
Sai, along with the rest of Team Yamato joined Kakashi's 8-Man Squad in their search for Itachi, and later Sasuke.

Invasion of Pain arc
Sai was present along with Team Kakashi and Tsunade when Jiraiya's death was revealed to Naruto. Later, he is sent out with Yamato and Anko Mitarashi to locate and capture Kabuto. Through his survellience skills, he is able to locate Kabuto.

Shippūden The Movie 2: Bonds
Due to Sai's ability to create flying mounts for himself with his Super Beasts Imitation Picture Technique, he served a double function as recon scout and first counterstrike against the Sky-nin attackers. He showed himself to have great proficiency in aerial combat, taking down the admittedly sparse forces the recouperating enemy sent out against him with relative ease. He even noted that he was getting bored from the enemies' poor performance.

Trivia

 * It was commented on by Sakura, Ino, and Naruto that Sai resembled Sasuke physically. However, Sai and Sasuke had totally different personalities and Sai has extremely pale skin and short hair compared to Sasuke.
 * As Sai was formally a member of ANBU, he referred to Kakashi as his Senpai out of respect.

Quotes

 * (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 Naruto) "Please stop staring at me. Or I'll have to hit you."
 * (To Kabuto) "If people change...then so can I. But some things never change. Bonds. I'd like to learn more about them."
 * (To Naruto, Sakura and Tenzo) "Sai is the name I was giving for this mission...I'm nobody. I am a tool for Lord Danzo. I don't exist''"