Based on the erotic game by TinkerBell.

A university student Matsubara Ryoji was living alone. But he had uncle near the aparment, and he often went to his house. Because the uncle was busy and often absent, for his wife and daughter, Ryoji was reliable person. On the other hand, Ryoji secretly fell in love with the aunt, Kasumi.

One day, the neighbor houses were robbed while they were absent. The uncle proposed Ryoji would leave the aparment and live together.

(Source: AnimeNfo)