Kanrinin-san wa Miboujin

The protagonist, Hirayama Riku, is a poor student who is living at a run-down apartment. There are 3 reasons why he is living here: the university is near, the rent is cheap and most of all, the manager is cute. However, she is nearly a decade older than him. Also, although she is a widow, she still thinks about her husband even now. One day, a beautiful woman moves next door and discovers his love for the manager. "So you like the manager huh? Then big sister will help you!"