Kanojo ga Cafe ni Iru

A 16-year-old high school girl, Michiru Isshiki, has cool childhood friends--- her next door neighbors, Ryouhei and Shuusuke Kuwa. Shuusuke, the same age as Michiru, is a pure-hearted, passionate rugby player. On the other hand, Ryouhei, three years their senior, works as a model, and is the campus crush. Because Michiru is a pure-hearted person, Michiru opposes the playboy Ryouhei, but she realized her true feelings when she saw a kissing scene between Ryouhei and his girlfriend, Youko!

(from mangaupdates)