Kusunoki Azuki and Daizu are close siblings who live in the Arisuno apartment complex. Their next door neighbor is Azuki's childhood friend Tachibana Chika, who has feelings for her. One day, two brothers who are close to their ages, Hiiragi Mizuki and R

The manga centers on Sui, a girl in her third year of junior high. She doesn't really get along with her older sister's boyfriend, Midori-kun, since he always treats her like a kid and makes fun of her. But Midori-kun is suddenly asked to be Sui's home