Birthdate: November 25
Age: 17
Ninja Registration Nº: 012420
Blood type: A
Height: 172.1 cm
Weight: 53.3 kg
Current rank: ANBU

Sai is the replacement of Sasuke Uchiha in Team 7. The name "Sai" is given to him for the purposes of joining the team, his actual name being unknown. He was recruited at a young age by Root, which trained him to have no emotions so as to make it easier for him to accomplish missions. This lack of personality causes Sai to meet with hardship upon joining Team 7, as he makes the mistake of insulting the other members in an attempt to seem sociable. He tries to seem more caring 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. Wanting to experience bonds for himself, Sai sets out to make as many bonds as he can. His initial attempts consist of giving people pet names, though his habit of calling people as he sees them ("fat", "ugly", etc.) finds little success. Realizing that people dislike hearing how they actually look, Sai begins to say the opposite of how he sees them, such as calling Ino Yamanaka "beautiful". With names proving successful, Sai has since made attempts to be helpful to others, though his attempts have thus far been unwanted by those he is trying to help.

Sai is a talented artist, and claims to have drawn thousands of pictures. Despite the magnitude of pictures he has drawn, his lack of emotion makes it impossible for him be inspired to give something a title, and thus all of his works are nameless. Sai's drawing ability is also the source of his jutsu; by drawing things with a brush on his scroll he is able to bring his creations to life, giving them an increased size and the ability to move. His Super Beasts Imitation Picture (超獣偽画, Chōjū Giga) allows him to create birds that he can use for flight and lion-like creatures that he can use for attack. Likewise, by creating an Ink Clone (墨分身, Sumi Bunshin?) 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 arriving, giving Sai an easy way to communicate.