Good Luck! Ninomiya-kun

Shungo Ninomiya, a high school student, lives with his older sister Ryoko when she's not away fighting as a mercenary. Mayu Tsukimura, a succubus, and her brother Mikihiro, an incubus, move in with the Ninomiyas at Ryoko's request. Mayu suffers from androphobia, and Ryoko tasks Shungo with helping her overcome it. This involves shared living arrangements, including sleeping and bathing together, which complicates their situation.