Futaribeyaふたりべや (Japanese); 妳我的双人间 (Chinese); A Room For Two; Room for two persons (English)

From NHFH Scanlations: Sakurako Kawawa has moved into a boarding house to attend high school, excitedly waiting her first meeting with her new roommate. And who should arrive at her door but Kasumi Yamabuki? Kasumi is absolutely stunning, but she marches at the beat of her own drum. Her carelessness awakens the "big sister" inside of Sakurako.