Ijiranaide, Nagatoro-san

Naoto Hachiouji —our spineless— MC (Known also as "Senpai") is a second-year high school student and a loner who spends his afternoons at the Arts Club room. He attracts the attention of one of his schoolmates, a sadistic freshman girl named Nagatoro. However, in between the bullying and teasing, something else begins to blossom.

A lovey-dovey(…?) story between a shy nerd and an S-Dere (Sadistic Tsundere) begins.

Links:

• Alternative Official English - K Manga (U.S. Only), Kodansha