Hankouki na Kareshi

Nagisa Takeuchi is a college student who has been tormented by her first love from five years ago.

One day, I happened to attend a blind date party, where I was spotted by the most flirtatious-looking guy that I, a so-called "complicated girl," disliked the most.... I found myself taking him to the girls' dormitory! Who the hell are you?

(from mangaupdates)