Sai Yamanaka (山中サイ, Yamanaka Sai) is a Chūbu of Konohagakure's Yamanaka clan. Prior to this, he was an Anbu from Root. As per standard Root training, Sai was conditioned to remove all emotions and as such, had difficulty connecting with others. When he is added to Team Kakashi as a replacement for the rogue Sasuke Uchiha, Sai begins to learn more about people's feelings and tries to develop his personality and identity by forming genuine bonds and rediscovering the emotions he was taught to suppress.
Sai was orphaned as a child and recruited into Root, a secret branch of the Anbu under the leadership of Danzō Shimura. 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, the final step in Root training called for the two to fight to the death to eradicate all remaining 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 but Shin, knowing that he was dying anyway, told Sai to report to Danzō that he had killed him in battle. Before dying, Shin told his brother that he had to suppress his feelings, and to 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. At the time he was assigned to Team Kakashi, the last assassination he performed was of Unmo Samidare. In the anime, an attempt to gain a powerful fūinjutsu after seeing the Third Hokage sacrifice his life in an attempt to defeat Orochimaru, led Danzō to supervise 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.
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. In the anime, it was shown from his Infinite Tsukuyomi dream that his greatest desire is to fully rediscover his emotions and connect with as many people as possible through it.
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, something he mentions is due to his still lacklustre understanding of both his Team 7 teammates and emotions in general and he would come to regret when it lead to Sakura's suicidal attempt to stop Sasuke, feeling that as if he was a true friend, he should've found another way. Sai holds Naruto in high regard, and tries to assist Naruto whenever he's going through hardships however he can.
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, forming a closer bond with Ino, showing more forwardness in such acts as asking her on a date and holding her hand affectionately. This ultimately led to them forming a family. Through all this, Sai has completely come to reject the teachings of Root, accepting that Danzō's intentions, while genuine to protect the village, were misguided and only led to more suffering.
Sai is shown to care greatly for his family, as he has begun training his son in his artistic-ninjutsu, finding humour in Inojin's cruder drawing. Sai also has developed strong parenting skills, being the one who's reprimanding Naruto for not holding back enough when he tried to counter Boruto's shadow clone with his own. His compassion for his son's happiness was also shown from not wanting to hurt any of his friends, regardless of the circumstances.
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.
A decade 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.
Sai has proficient skill in the Earth Release nature transformation, able to conceal himself underground without disrupting the surface of the earth. He can also use the natures of Fire, Water, and Yang Release.
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.
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.
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 opponent wielding a larger weapon.
As a Root Anbu, Sai has keen observation skills and is also skilled in kenjutsu, wielding a tantō in battle, with which he can deliver swift slashes at the opponent. He is also very proficient with the Body Flicker Technique, capable of surprising even highly-skilled shinobi with it.
Sai eventually married Ino, and had a son with her, named Inojin, whom Sai helps train to become part of the new generation Ino–Shika–Chō, with assistance from his wife.
As mysterious attacks began happening more commonly and expanding in area, Sai was called to help in the investigation. He later found evidence to suggest that the real goal of the perpetrator was to harvest people's chakra. It was also discovered that the Wood Release was possibly involved. As Root had a history of conducting its own secret research on the famed power of the First Hokage, Sai went to research more of the disbanded Anbu unit alongside Shikamaru. As the attacks continued to occur, Sai intensified his efforts. While Naruto told him to calm down, Sai was determined to save the potential culprit from following the misguided ideology of Root.
Later, a strange release of chakra began spreading throughout the village. As it showed a similar nature to the chakra of the rampages, Sai went to act. His investigation led to an old facility of Root, which turned out to be the hideout of the late-Tanuki Shigaraki, one of Danzō's top researchers and most loyal followers. Putting the pieces together, Sai remembered that Tanuki was in charge of creating an ultimate weapon made from the First Hokage's cells. While looking around the demolished building, he found a picture of Tanuki, with a young girl Sai immediately recognised as Sumire Kakei. After reporting his findings to Naruto, Sai and his unit went in search of Sumire, who disappeared from the hospital. Sai soon found her and subdued her. While preparing to take her in, she unleashed the Nue. The rampaging beast gave Sumire the chance to escape while Sai and his unit attempted to hold off the beast. Kakashi soon appeared, severing its tail, only for the creature to sprout dozens of smaller tails and steal people's chakra. As Kakashi organised the unit to hold off the creature, it suddenly teleported away.[
Kakashi deduced that the creature acts differently from normal summonings, naturally existing in its own separate dimension. By morning, Sumire returned from the separate dimension along with Boruto and Mitsuki. Sai, still sympathising with Sumire's history with Root, offered to help her forge a new brighter path. Having let got of her anger at the village thanks to Boruto's words, Sumire accepted Sai's offer and peacefully turned herself in. Sai promised Boruto that she would be fine.
Later, Sai discussed the future of Sumire with Naruto and Shikamaru. Sai also removed Sumire's Academy records to weigh in their options.
Sarada Uchiha Arc
The week before Inojin's Academy graduation exam, Sai practices his signature technique with his son. When Naruto and Boruto Uzumaki sparing session interrupts them, Sai tells the Seventh it's petty of him to consider using multiple Shadow Clones against Boruto. Afterwards, Inojin tells him his taste in art is ancient.
Versus Momoshiki Arc
Sai is put in charge as the proctor of the first phase of the Chūnin Exams with Shikamaru Nara. For the test, Sai asked the participating genin teams to answer a true or false question on a novel series about ninja strategies. To everyone's surprise, Sai revealed neither answer was correct and all the teams were sent hurling into a lake of ink; those who didn't "turn black" passed. Sai explains that the purpose of the test was to test everyone's reaction in a critical situation, and his son, Inojin, comments to his team that only his father could come up with such an idea.
Mujina Bandits Arc
n the days following the Ōtsutsuki attack on the Chūnin Exams, Sai and Ibiki Morino report that Katasuke Tōno was under mind-control to Naruto, and suggest it's likely that the perpetrator was after Konoha's technology. Afterwards, Naruto has them look further into the matter.
Later, after the Mujina Bandits were captured by Team Konohamaru, Sai and Ibiki were tasked with interrogating the leader, Shojoji. While arrogant at first and demanding compensation, the timely arrival of Sasuke and his dark reputation quickly swayed Sojoji to talk. While knowing very little, Shojoji explained that mark on Boruto's right palm was identical to one used by an organisation called "Kara". He also said that the marks' nature is vaguely similar to Orochimaru's Juinjutsu.
- (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."