From MangaHelpers:

Sick and tired of being bullied in school, Kazu decides to get the help of the devil. Being the lazy and worthless pervert that he is, instead of standing up for himself, he attempts to curse them and ends up actually summoning the devil. Cel is still an intern devil, learning the ropes until she can become a full fledged evil being, but until then, she has to deal with Kazu. In return for granting his wish, Cel will take Kazu’s soul as a payment but things don’t go quite smooth. [vyc]