So in this manga there is a male devil who hasn't reached his quota of soul harvesting by contracting humans, so he goes to earth to try and get a contract. Then he met this girl who said something along the lines of 'be my boyfriend', which he objects because that would be time consuming and shes like 13. But he has to follow the contract and although it is loosely romance it is more like parental care, and he learns to care for her over the course of the manga