I'm looking for a hentai about a guy who has a chance to have sex with a popular girl. At the crucial moment he fails(I forget how). The next day at school she writes on the chalk board about him sucking at sex. He goes to the roof to be alone or jump(I forget) and this chick that's up there has sex with him and then they go back to the classroom and say hes not bad at it, shes just a cold fish.

Feed your head.

Kassen soubatsu by Kino Hitoshi