Sai

Sai is one of the main supporting characters in the Naruto franchise. He serves as Sasuke's replacment in Team 7. He is an ANBU-level shinobi of Konohagakure and is from the disbanded faction: Root. His well-known jutsus are Ink Clone Technique and Ink Mist Technique.

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 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.

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, something he mentions is due to his still lacking understanding of both his Team 7 team-mates and emotions in general. 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, as he ultimately formed a family with Ino. He has also begun training his son in his artistic-ninjutsu, finding humour in Inojin's cruder drawing.

History
Tsunade was pressured into making Sai Sasuke's replacement in Team 7, but Naruto and Sakura were also met by a new group leader, Yamato. They set out to meet Sasori's spy and get information from him, possibly even capture him for further questioning. On their trip the group came to know each other better, but Naruto had already previously met Sai, who attacked him in Konoha. Although Sai exclaimed that he merely wanted to test his teammate a little bit. Sai had the habit of insulting others (unintentionally) and saying what's on his mind, not considering others' feelings... or rather, not understanding them, which caused alot of animosity between him, Naruto, and Sakura. But Sakura was intrigued by Sai and sought to learn a little more about him; she found out that he's a painter and he told her that he was trained as a small child not to have any emotions and it's hard for him to understand emotions or even the bond that Sakura and Naruto have with Sasuke, admitting that he didn't even cry when his brother died. He also informed her that he has been trying to simulate emotions after learning what he reads in books, but nobody believes them. She came across a picture book that Sai was working on and asked if she could see it, but Sai told her that he didn't want anyone seeing it.

Sasuke & Sai Arc

Back on their mission, the spy turned out to be Kabuto who was secretly a double agent, actually working for Orochimaru. He and Orochimaru planned on killing Sasori right then and there and that's when Team 7's plan fell apart, but Kabuto and Orochimaru too realized that they were tricked. The Kyuubi's chakra began to flood out of Naruto as he sprouted four tails and attacked Orochimaru, scaring Sakura. Sakura and Yamato had a brief scuffle with Kabuto, but Sai was mysteriously absent in all of this. Kabuto informed Team 7 that he and Orochimaru don't want to fight them, saying that Akatsuki has been a thorn in their side and they're hoping that Team 7 can take out more of their members for them. With no more threat, Yamato took the opportunity to suppress the Kyuubi's chakra within Naruto. While that took place, Sai confronted Orochimaru and offered an alliance, giving Orochimaru an envelope that he was ordered by Danzo to give to Orochimaru. The three took off, but Yamato's Wood Clone followed. Team 7 soon gave chase after Sakura found Sai's picture book laying on the ground. The team started to go through it, trying to figure out it's meaning and find out why he'd betray them. On their way, they came across Sai, having been hung by Orochimaru and Kabuto. This however was a trick meant to halt their pursuit, they followed still.

At Orochimaru's hidden base, it's revealed that the envelope contained detailed information on many powerful figures within Konoha and Danzo was hoping that they could help each other overthrow Tsunade since Danzo hates her and wants to be the Hokage. Orochimaru is intrigued and has Kabuto put Sai in a locked room. Team 7 are going through Sai's book and they notice that it stars two characters, both of their "stories" start on opposite sides of the book and seem to meet in the center, however the center pages are missing. They notice that one of the characters is Sai who is shown fighting different people on each page, and every next page shows him with something his previous opponent owned. This trend was the same with the other white-haired character, but they had no idea who it was. Team 7 would find Orochimaru's base and find Sai. There, they talked with him and he revealed what he told Orochimaru and what the true plan is... Orochimaru is a threat to Konoha and Sai was supposed to relate any new information about him back to Danzo so that Root can kill him. They talked a little more about Sai's picture book and he reveals that it's his brother in that book... or rather, they called each other "brother." Root is made up of orphans that Danzo trained to be perfect soldiers. Sai revealed that he can send messages to Danzo because of his ability to turn his writings into small animals and send these messages to Danzo safely. Sakura asks if he's the one that killed his "brother," but Sai informs her that she's incorrect and that he died of illness. He said that he came from the two where Zabuza came from She tries to convince him that Sai did have a bond once and that he should understand what her and Naruto are going through. Sai feels like he may understand a little and agrees to help them find Sasuke, and they split up. They have tied Sai and interrogated him about further information about his mission. Kabuto then appeared believing that Sai was tortured and needs to be rescued. The joined forces of the Team 7 was good but quite not enough. Though, as kabuto unties Sai, he attacked Kabuto and declared his betrayal to Orochimaru saying that he wants to know how Naruto feels for his friend Sasuke. Sai then helped the Team 7 look for Sasuke after some interrogations to Kabuto. Due to the hideout's large area, the Team 7 have to be divided. Naruto was with Sai while Sakura is with Yamato. Sai and Naruto then decided to have a rest as they tell stories about each other. Sai compares Narutio to his brother because of many comparable things between the two of them. As Sai reminisces his memories with his brother, Sai finally was able to remember what he is about to draw before his brother passed away. He get his picture book and drew his brother holding his hand and they were both smiling. Despite the happiness that he feels, Orochimaru then appeared and fought them asking Sai who is really his companion. Naruto decided to continue fighting the aforementioned villain and Sai was assigned by Naruto to look for Sasuke. Sai drew a bunch of rats to seek for Sasuke as they seek every corner of their hideout. At last, he have found where Sasuke is sleeping. Meanwhile, Yamato and Sakura have helped Naruto against Orochimaru but he only teleported away to look for Sai. Yamato then looked inside Sai's backpack which he left in the area. He have found out about his Bingo Book. That book is a book where assassins list their targets. The team was surprised as they turn the page and found out that Uchiha Sasuke was one of their targets.

They open every door in Orochimaru's lair trying to find Sasuke, but Sai is the first to find him. Sasuke asks why Sai would disturb his sleep, and Sai informs Sasuke that he's supposed to kill him. Naruto and Sakura hear a large ruckus and go to see if Sai's ok. They find out that Sai wasn't only supposed to kill Orochimaru, he was supposed to kill Sasuke too... since he's a threat to Konoha aswell. Naruto attacks Sai, but Sai informs them that he was supposed to kill Sasuke, but he decided not to, wanting to learn more about "bonds." They find Sasuke watching them from up high and after a brief talk, Sasuke attacks Naruto but Sai stops him from killing Naruto. After a brief scuffle, Kabuto and Orochimaru appear and stop Sasuke, telling him that they have a temporary truce with Team 7 and leave.

Team 7 later return to Konoha. They have reported to Tsunade about the events that happened during their mission. Yamato then have revealed Sai's relationship with Danzo which angers her. Sai then went to Danzo and asked him if he can stillstay with the Team 7. Danzo agreed. He then became very serious in studying about making more friends. He have found out that the best way to have friends is to drop the honorifics and make nicknames instead. After conversing with Sakura and Naruto, based on the book, he have called Sakura ugly and led to her being mad. Naruto have tried to stopped Sakura's anger but as only hurt. She punched both of them leading Sai and Naruto's cheeks to be hurt. The team then proceeded to Kakashi's room wherein they had a conversation about their mission. It was the first time for Sai to meet Kakashi. Sai meets Chouji and Ino. Sai having former encounters with the team havefound it uncomfortable to talk with them. However, because of the book that he often reads, he decided to try to became nice to them.Sai thinks to himself that a book said that a good way to make friends was to give people nicknames, so he was about to call Chouji a fatass... but Naruto stopped him. Seeing Chouji get defensive and realizing what Sakura did earlier when he called her "butt ugly," he realized that people don't like to hear the truth, so he calls Ino "beautiful," which makes her blush... but angers Sakura.