Stalker Otoko ga Suki na Onnanoko no Himitsu wo Shiru Hanashi

Tadashi Kazumi is so in love with Misora Amakawa, a girl in his class, that he has been researching everything about her. It may seem like a bit of a stretch, but he seems to think that unrequited love and stalking are two different things.

Note: Chapter 1 was originally published as a one-shot in Young Animal, with chapters 2 and 3 being drawn later due to the manga's popularity among readers.