Tomodachi no Oneesan to Inkya ga Koi wo Suru to Dou Naru no ka? (Associated Names)

A self-proclaimed unattractive gloomy high schooler, Hiramiya Reiji, everytime he goes to visit his close friend’s house, he gets messed around by his older sister, Sakuya. Drinking his drink as she pleases, barging into the bathroom, and crawling under his blanket in the middle of the night… Thinking that perhaps he has done something to…