Yup, I'm referring to the LN. And yeah, there is development between both pairings — Maou and Emi as well Maou and Chiho, but mainly between Maou and Emi. Only one of the girls end up with him. Depending on who you're rooting for, you may end up disappointed or not. If you haven't even begun to read it, then I don't suggest going into it for the romance aspect alone. It's not the main focus and I honestly don't think it had a satisfying resolution regarding the topic, for either pairings.