Takuya is a university student. He plans to earn money so that he can go travelling with his girlfriend, Yuki. He starts working as a live-in home tutor at Otoha’s house. One day, he finds a hole in the wall. He looks into it and sees Kaori, Otoha’s mother, doing her hair. It seems it is Otoha’s parents’ bedroom. Who made this hole? What for?