While rummaging through his grandfather's attic, Hikaru Shindou discovers an old go board. When he touches it, a mysterious voice speaks to him, and he soon passes out. Upon waking, he realizes the voice still lingers and belongs to Fujiwara no Sai, the ghost of an ancient go master. Once a go instructor for the Japanese Emperor during the Heian Era, Sai's love for the game transcends time and space, allowing him to keep playing as a spirit. Sai's ultimate ambition is to achieve a divine go technique that no one has ever mastered, and he hopes to do so by playing through Hikaru.
Though Hikaru has no interest in board games, he reluctantly goes along, making moves as Sai directs. But after meeting the young go prodigy Akira Touya, a spark of passion for the game begins to grow within him. Inspired by his new rival, Hikaru's journey into the world of go has only just begun.