A spirit from the Heian era of Japan and mentor of Hikaru Shindo. Sai continually plays Go in attempt to one day play the divine move (also known as the Hand of God). In the manga and anime, Sai had possessed the real-life figure Hon'inbo Shusaku and through his body, became a renowned Go player. Sai holds a rivalry towards Koyo Toya (a.k.a. Toya Meijin) and through Hikaru persuades Toya to have a game with him.<br /> <br />
