Fujiwara no Sai (藤原佐為, Fujiwaranosai) is a spirit from Heian period, Go prodigy. First resided in Honinbou Shuusaku's body and played as him, giving him a fame, later in Hikaru Shindou's. He's one of those who are the closest to playing a Hand of God.
Sai is tall man with very long, black-purple hair tied with a red ribbon, and purple eyes. He wears usual Japanese clothes from Heian period, consisting of a hat, red-purple kimono and white robe on it. He has red earring in his ears.
The fan he carries seems to be a maiougi, or Japanese dance fan.
Sai is extremely emotional person, who often acts childish and has great mood swings.
Sai was originally one of the Emperor's Go instructors. Once, the other instructors decided there should only be one instructor, so the Sai and he played a game to decide it. In the midst of the game, he was wrongly accused of cheating, so his game went off and he lost, and therefore banished from the Kingdom. Filled with despair, he drowned himself in a nearby pond. Hundreds years later, as the ghost, he met Kuwabara Torajirou, who, after realizing Sai's talent, let him play Go in his place. He quickly made Torajirou a genius and achieved Honinbou Title. However, Torajirou ended up dying young and thus, Sai was confined in the old Goban as a bloodstain (which was from ill Torajirou).
Sai is first seen—or rather, heard—when Hikaru touches his grandfather's 'cursed goban' (the board on which you play Go). His appearance causes Hikaru to start in shock, causing him to fall down to Akari's surprise. He initially appears to be a serious and effeminate person, an impression soon proven wrong: during a history test that Hikaru has to sit through, Sai continuously fails to stop himself from calling out. He then reveals the consequences of his being a ghost to Hikaru, as well as his history with Honinbou Shuusaku, otherwise known as Torajirou. He then reveals his desire to achieve the 'Hand of God'. When Hikaru tells Sai his desire to not play Go, Sai's intense feelings of sadness overwhelm him, causing Hikaru to run off, vomiting. After another few 'vomits', Hikaru reluctantly agrees to play Go.
After school, Hikaru and Sai go over to Hikaru's grandfather's house to play Go, where Hikaru makes a bet with his grandfather that he'd beat him. However, after a few hands, Hikaru's grandfather tells Hikaru to "come back in 6 months". Hikaru then goes back to his home and finds out Sai's usefulness in History. He then questions why Sai appeared to him "who has no interest in Go". Hikaru goes to Go classes to learn the basics of Go but finds it tedious, and boring; but the Pro teaching the class shows him practically.
Sai's Go is complicated but on very high level. Sometimes, he places stones that appears to be neither defensive nor offensive. His style of playing is quite old-fashioned, playing the same as during Honinbou Shuusaku's era.
- Because of his feminine features, long hair and his extremely emotional behavior, Sai is often mistaken for a female. These characteristics would actually be regarded as signs of intelligence and wisdom during his time.