Musunde Hiraite

A collection of high school love stories, each chapter featuring a different student. For example, Hiro has a crush on a cute upperclassman girl, but she has rejected his advances 15 times! Will Hiro be able to find a way into her heart? His friend Akechi keeps a notebook of information on all the girls at school, but when he goes after the secrets of an incredibly quiet and shy girl, will his interest become more than professional curiosity?

(Source: MangaHelpers)

Each chapter focuses on a different character, although they are all related through being classmates.