Sai, the Go genius, was born approximately a thousand years ago in the Heian Dynasty. At that time, Sai was the Go teacher of the emperor. One day, the other Go's teacher challenged Sai to decide who was better. During the match, Sai was accused for cheating, while actually it was his opponent who cheated. That incident caused Sai to lose his concentration and lost the match. Sai was driven away and he ended up commiting suicide.

However Sai's spirit was unable to rest, as he was still want to play Go. Hundreds years later, Sai came to possess Honinbo Shusaku. With Sai's skill, Shusaku become the best Go player ever in the history. Unfortunately not for long, as Shusaku died of serious illness at the age of 34.

Sai stayed in the Go board for another 140 years until Hikaru found him. Finally Sai was able to play Go again. A thousands years of Go skill still shine brilliantly, even in the advance world of the 21st century.

Personality

Sai often whines and cries, especially when Hikaru refused to let him play Go. In character, Sai is righteous and treasures friendships. However Sai is totally a different person when he plays Go. He is calm and sometimes merciless. ( He had slashed tons of his opponents ^^ )