Bondage Mansion (2000)

Reika Mimura came from a wealthy family and never wanted for anything. Then, her uncle died and left her with a single unusual wish: find a previously unknown cousin and allow him to live in the family home with her. Unfortunately, she is woefully unaware of her family history: while Reika is a normal girl interested in sex like anyone else, her family has for years practiced dominion over its women. This puts her in the middle of a bizarre ritual between her current boyfriend and her sadistic cousin: the one who breaks her is the one who gets the house and the money. Certainly Reika had no idea what her uncle had in store for her!