Imaizumin Chi wa Douyara Gal no Tamariba ni Natteru Rashii ~OMAKE~

Imaizumi is a high school boy who lives alone in his apartment for a reason. He has a secret that he can’t tell to anyone. And the secret is that he lives with the three most attractive gals from his school, Hamasaki, Kurumizaka, and Sasaki. He spends his day playing, talking and getting physical with the girls, each with her own quirks. He can get used to this carefree and naughty “youth”…?

(Source: Ganma!, translated)

Imaizumin's House is a Place for Gals to Gather EXTRA Contains some backstory. MUST READ, if you want to follow the story.