Ringo, a kindergartener, adores his two 'older brothers' who live in the apartment building his grandparents own. However, these two are actually an angel and a demon with a complicated past. The angel, who once saved the demon from being killed, is shocked by the demon's despair and sense of purposelessness in life, and decides to help him find his place in the world by moving to the human realm together. The pure-hearted angel, who knows nothing about love, suddenly starts living with the demon. They have a heartwarming life, with Ringo becoming attached to them as they invite him into their home. But the wild and handsome demon transforms into a terrifyingly lewd monster on nights of the new moon...