Hatachi made ni Nantoka Shitai

Yui, a reclusive college boy, is actually an incubus. If he does not regularly suck sexual energy from his childhood friend Miki, he releases pheromones that cause the girls around him to go into heat. Furthermore, he has a weird condition that causes him to suffer food poisoning with energy from other girls. According to incubus lore, he must have sex before age 18 or he will die, and now he has only six months left before his time limit...! They like each other, but their path to love will be complicated... (Source: Manga Mee, translated)