Reika Uehara lives with Yukio Mimura in their family mansion, sharing mutual romantic feelings and an anticipated future together. Their peace shatters when their cousin, Hayato Mimura, arrives demanding they leave the property. Facing this conflict, Hayato invokes a historical contest used by their fathers to decide mansion ownership. This contest focuses entirely on Reika, requiring both male cousins to compete in being the first to psychologically and physically "break" her through systematic sexual domination and training games.

Reika becomes the unwilling participant in these acts, subjected to intense physical and psychological pressure designed to force her submission. Her expressions reveal profound distress, anguish, and involuntary physical reactions throughout the ordeal. The outcome of the contest depends solely on which cousin succeeds in breaking her will, determining who gains permanent control over the mansion.