Jutten manga

Jutten! summary:

Jutten! is about a boy who goes to his first day of high school thinking it'll be full of awesome meetings with sexy girls and whatnot, but instead has a lot of bad luck and gets peed on by a dog, amongst other things. A girl who uses her bike to drive over his ass sorta helps him and gives him a handkerchief with a 10 yen coin in it (hence the the series' title) and ... Then 10 yen coin contains a spirit who says she will grant the boy's wish of wanting to be together with the girl but the spirit can only cast magic worth 10 yen.