Kinbaku no Yakata: Ryakudatsu - Season 1

Born into affluence, Mimura Yukio has led a life free of hardship. His father's dying wish, which he dutifully obeys, is to locate an unknown cousin and grant him residence in the family estate. Yukio's gentle nature leaves him ignorant of his lineage's connection to sadomasochism. The cousin, Hayato, arrives with designs not only on the mansion and its wealth, but also on Yukio's girlfriend, Reika. To prevent the exposure of his family's secrets, Yukio is coerced into a sexual contest. The terms state that whoever first breaks Reika's will shall inherit the property and fortune, making her the central figure in their struggle.