Manabu, a ronin student who was living at home with his parents, was wandering around the neighborhood engrossed in an exploration-type monster collecting game that has recently become popular. One day, guided by the game, Manabu comes to an empty house that has rarely been visited since ancient times, and notices a woman's voice coming from the back room. When she timidly peeked in, she saw Yuka, a married woman with whom her parents had been close friends.