Boku x Kano

Summary

Hayashi Shoutaro is an otaku and a student who sucks at studying, the results showing on every test; if that wasn't the worst, he makes promises like the one who scores the lowest has to clean the classroom by themselves. In his classroom there is a girl he likes, Kanda Yayoi, who always scores the top and is popular among boys and girls. After going home from cleaning the classroom, he's met by his perverted/otaku sister who has him cross-play (cross-dressing cosplay) to go to an anime merchandise display, where he meets Yayoi who is also an otaku and she falls in love with his cosplay-persona...? (Source: mangaupdates)