Hikaru Shindo, an ordinary sixth-grader in Japan, finds an old Go board in his grandfather's attic that holds the ghost of Fujiwara-no-Sai, an ancient Go master who once taught the game to the Emperor of Japan, and somehow Sai becomes part of Hikaru's consciousness, making them an unstoppable Go-playing team.
When Hikaru convinces go master Toya Meijin to play Sai online, the meijin raises the stakes: if he wins, "sai" must reveal his true identity; if he loses, he will quit the game forever! Then, Hikaru challenges himself by playing Kurata 6 dan. How do you win a game in which both players use the same color stones?!.
Hikaru Shindo, a schoolboy whose consciousness houses the spirit of a master Go player, struggles to turn his losing streak at the insei school around in time for the Young Lions Tournament, where he could have a chance to play against his rival, Go prodigy Akira Toya.
Hikaru, gaining expertise from the spirit of the game master Fujiwara-no-Sai, agrees to play Toya Meijin online, but if he loses he must reveal his identity, then he takes on an opponent who uses the same color stones.
Hikaru Shindo, who stumbled across a haunted Go board and lives with the spirit of a master player, Fujiwara-no-Sai, in his mind, refuses to let Sai play, which causes the inner coach to vanish, leaving Hikaru to fend for himself.
Isumi returns from his foreign training with unique methods of handling the stress and mental strain of competition, but when he challenges Hikaru to a rematch, his friends wonder how he will fare in battle after such a long break.
Hikaru learns his rival, Akira, has landed a place on Japan's team for the Hokuto Cup and battles for one of the two remaining spots, while the Go world is shocked by Akira's father's retirement.
Hikaru faces Korea's top Go player, Ko Yong Ha, in the Hokuto Cup tournament. The outcome will affect a new generation of Go players and may even change the game itself.
