Koisuru Succubus no Ikenai Jijou

Synopsis

Twin girls, Oona and Hooru, come to the house of Takeuchi Kou, a skilled male porn star. They may look like ordinary little girls but they're actually succubi who feed on sexual desire. They're here to be with their beloved Takeuchi. However, a succubus can't truly be with a human because of their species difference. But there is a way for a succubus to become human... by collecting "abstinence orbs." To generate abstinence orbs, he must tease them to near orgasm but never let them actually come. Let the abstinence survival battle begin!!! (Source: Comic GammaPlus, translated)