Responses
I not sure if this is what your looking for:
http://www.mangago.me/read-manga/obaka_chan_koigatariki/
I've only read the first few chapters but that was a long time ago, but it seems to vaguely fit your description (≧∀≦)
Yes yes thanks!!!!! I think it is the right one. I have lookt for it for sooooo long ヾ(☆▽☆)
Some time ago I was reading a romantic manga abaout a girl starting in a new shool, she ends upp in a class whit a troubelmaker/deliquent that falls in love whit her but she likes the "cool/perfect" classpresident and he agres to go out whit her. But the classpresident has a grude/rivalety with the deliquent and ends upp useing her, he cruely dumps her and by doing that hurt the deliquent. At first the classprez dont feel anythig but later falls in love with the girl for real but she wont belive him and so the "competion" about her fellings begin.
Ps. Later it is reviled that the girl was a deliquent gang leader? or something befor she moved shool.