向かい部屋の美巨乳女を彼氏に内緒でひたすら性交 いいなり性欲処理肉便器に堕とすまで…

The protagonist often observes his neighbor, Rin, having sex with her boyfriend, and he begins to fantasize and fap to her regularly. She is way out of his league, but eventually he can’t resist the temptation and moves to get the real thing.