Sei Has Forgotten Love

Sora Amazawa, a high school freshman, had her first love, Hoshi Kiritani, a year older than her, whom she fell in love with during the summer of her fifth year. He went abroad and they drifted apart, but they promised each other that their love would never change until they met again under the stars five years later. They meet again in high school, but Hoshi, who used to be a tough guy, has become quite a popular boy!　Moreover, he doesn't remember Sora at all and has lost all memories of the past... (Source: Kodansha, translated)