Sai Fujiwara no  

, 藤原佐為

In the manga and anime series "hikaru no soko," sai is an artificial intelligence spirit from japan's heian era who serves as a mentor for hikaru shindo, a young go player. sai possesses the consciousness of honinbo shusaku, a famous real-life go player, and uses his body to become renowned in the game. despite this, he harbors a rivalry with koyo toya (also known as toya meijin) and through hikaru's persuasion, arranges for them to play against each other.