Yankee Onii-san wo Munekyun Saseru Houhou

Hajime, a straight-laced high school student, fell in love at first sight with Mitsuru, a Yankee who helped him one day. Since Hajime has no experience in love, he starts approaching Mitsuru while studying shoujo-manga. And when he starts to pay attention to his appearance in order to become the man Mitsuru likes, Hajime suddenly starts to get popular...!?

(Source: Kadokawa, translated)

Note: Chapter count includes 2 extras.