Shouma Maruze is a boy like many others, he spends his days in a quiet way, used as he is to taking care of the house instead of his super-busy mother. His childhood friend Nozomi lives next to Shouma, who seems to have a bit of a crush on him. One day, Nozomi's cat disappears, and Shouma helps searching for it. That's how he comes across a demon, Zelma, who claims to know where the cat is, and promises to rescue him. In return, Shouma will have to accept some sort of pact. The boy accepts without hesitation, does not imagine that in doing so Zelma will remain at his side on a permanent basis. From now on, magic, transformations and fights will be on the agenda!