Hisui

Hisui is one of the five main heroines of Tsukihime alongside Arcueid Brunestud, Ciel, Akiha Tohno and Kohaku. Her character image song is PARADE, performed by Soft Ballet.

She is the younger of the two twin maids in the Tohno mansion, the other being Kohaku. Her name, Hisui, is the Japanese word for jade, referring to her eye color.

Background
Hisui was originally a member of a branch family of the Fujou clan, but was brought with her sister Kohaku to live in the Tohno mansion, because the Fujou clan had a special power of giving others energy. Makihisa Tohno needed this ability in order to keep control of his body.

Hisui, however, was never forced to utilize her abilities as a Synchronizer because of the pleas of Kohaku and instead found herself living as a normal girl. When Shiki Nanaya arrived to the Tohno house, at first he was unwilling to adapt to his new home, still traumatized for the death of his father. However Hisui was the one who encouraged Shiki to go out and play in the house. Her childhood was pleasant, and even though she is not naturally an active person, upon seeing Shiki playing so energetically she did her best to keep up with him.

After Shiki went to live with the Arimas, Hisui learned that Makihisa raped Kohaku so she becomes depressed. Kohaku, noticing this, promises Hisui that she will "take on her role" until she was cheerful again. Ironically, it is because of those words that Hisui is unable to return to her old self.