Mashiro is a guy with extremely bad luck. Apparenty it's because he's a special guy with a strong bond to demons. One day he meets Nijo an incubus who has collapsed due to hunger. They started living together with Nijo feeding off on Mashiro's life energy. Mashiro develops feelings for Nijo while Nijo took a while to realize his feelings. They become partners in the end. (Same concept as omegaverse bonds and pheromones being limited to a partner)
Tabesugi Kinshi!