Hikaru Shindou, a seemingly ordinary boy, accidentally awakens a spirit named Fujiwara no Sai while exploring his grandfather's attic.
Sai, a go master from the Heian Era, possesses Hikaru and uses him as a vessel to continue playing go, aiming to achieve a legendary level of skill.
Initially uninterested, Hikaru reluctantly agrees to play, guided by Sai's expert instructions.
However, Hikaru's encounter with the gifted young go player, Akira Touya, sparks a nascent passion for the game within him.
The anime follows Hikaru's journey as he begins to learn and understand go, driven by Sai's ambition and his own growing rivalry with Akira.