Gekkouzaka no Hanayashiki

Kashiwagi Yukiya lives with his son Yuuto in the home he inherited from his grandparents, a mansion surrounded by flowering trees. Takanashi lives there too, a holdover from the mansion's days as a rooming house for students. Long since graduated, he stays on because it's convenient to where he works. And because he's in love with Yukiya-san, whose secrets he's determined to get to the bottom of.