Character Arc
Fujiwara-no-Sai is the spirit of a Go instructor from Japan's Heian era who once served at the imperial court. Wrongly accused of cheating and driven to despair, he died with his greatest ambition unfulfilled: to find the divine move, the flawless, perfect game of Go. His longing was so powerful that his spirit lingered in a Go board for centuries, waiting for someone who could see and hear him.
When Sai awakens within Hikaru, he is at once joyful and desperate, finally able to play again through a living host. Elegant, emotional, and endlessly devoted to the game, Sai mentors Hikaru with patience and enthusiasm, delighting in every match. His pure love of Go and his childlike wonder make him one of the series' most beloved figures.
Sai's arc is ultimately bittersweet. As Hikaru grows stronger and more independent, Sai must confront the meaning of his prolonged existence and whether his purpose was to win the divine move himself or to pass his passion on to the next generation. His relationship with Hikaru becomes the emotional core of the story, blending mentorship with a profound sense of legacy and farewell.