Sex & Friend ~Osananajimi no Amai Nioi~

Masaki had known Mitsuru Ebina since they were little. The rumor at school was that they were going out. But in reality, they were always at each other's throats. Even so...Mitsuru was getting prettier each year, and Masaki couldn't help but notice. Then one day she came to give him a love letter one of the other girls had asked her to give him. Masaki had mixed feelings, but Mitsuru was as blunt as ever. And then he told her how he felt...

[From HgameZ.net]