Hanyuu was once known as the demon god of Onigafuchi (Hinamizawa) under her true name, Hainiryuun Ieasomuuru Jieda. She travelled with her clan to the Onigafuchi Swamp and tried to coexist with the human villagers there, but the Furude priest refused to cooperate. However, Riku Furude, the heir to the Furude shrine and inventor of the nickname "Hanyuu", fell in love with Hainiryuun and married her. They had a daughter named Ouka Furude, the first in a long lines of humans to carry demon blood. When the villagers of Onigafuchi became violent towards Hainiryuun's clan and could no longer tell who was a demon and who was not, they started to suspect and blame each other. Because of this, Hanyuu chose to become a sacrifice to atone for the villagers sins. She asked Ouka to kill her in what became the first Watanagashi ceremony, and by doing so, she 'buried' the villager's sins along with her.