This is going to be one of those emotional mangas. Guy gets drunk after his unrequited love gets married, Mikuni, and then ends up at a restaurant with the same name. A guy who works there let’s him stay the night at his place, where a continues crying and confuses him with his unrequited love. Turns out the guy, Mikuni Mayu, is a high schooler.
Toshishita Kareshi ni Hirowaremashita