Ren Kawasaki lives alone in a messy apartment-right next door to Mahiru and Mayuri Shiina, Mahiru a veritable angel who's the one of the smartest, prettiest girl at school and Mayuri is know as a devil due to her being somewhat different from her sister being very athletic that some people see it as deceiving due to her body type she's also conserved one of the prettiest girls in schoo.l When a chance encounter on a rainy day draws them together, Mahiru and Mayuri find themselves spending more and more time helping Ren get his life in order.