In the village where Rui lives, there was a certain custom. That is to decide a marriage partner not by one's own will, but by the village's rules. Rui broke up with her lover and decided to marry into the next village. Upon arriving in the next village, she receives an explanation from the village head. He says that each couple must perform a pre-marital ritual according to custom. She is taken to the ritual site and will undergo three days of training to cut off the impurities and desires of the world. Rui is tormented by Yu, who is taking care of her, with her body and anus. After being made to drink the semen of a man wearing a mask to purify the impure blood that came from outside, and three days later, the final ritual began…