Amane Sasamori

Amane is Riku's step-sister and love interest that disappeared during an accident two years ago. Eight years before the story, her father died near the same time as Riku's mother. Later after that, Shizuru and her moved in with Daichi as they were both students of his. Eventually Shizuru got closer with him and became married. Eventually, the sisters took on Daichi's family name, Amami. (Source: World Embryo Wiki)