I Don't Know Which is Love manga volume 2 features story and art by Tamamushi Oku.

Mei entered college determined to get a girlfriend, but she never expected so many girls to be coming after her instead! Still unsure which of her potential suitors is a keeper, Mei is suddenly hit with a straight-up confession from her serial-kissing senpai, Karin. Does that mean she’s completed her objective already…?!