Yukio Mimura and Reika Uehara live in there family's mansion peacefully. They have feelings for each other and are sure that they will live happy together. One night, Hayato Mimura, their cousin, arrives saying he wants them out of the house. Yukio doesn't agree with this and begins to think of any way they could settle this. Hayate comes up with a contest that their fathers did to win the house before them. That contest is to see who can be the first one to break Reika. Whoever breaks her, will be the winner and keeper of the house.

(Source: Anime News Network)