Hidamari Starlight

Aoi Yoneda has been taking care of his step-brother for ten years, ever since their parents died in an accident. Haruto loves his big brother, but he made a promise to himself to stay by Ao-kun's side as a brother until his 18th birthday. But then after? Only time will tell what happens between these two step-siblings.

(Source: Exiled Rebels Scans)