See You in the Sea / See In AO

The main character, Kyoya-kun, arrives at the oceanic city and school Endrud, where he will live and study for several years. Soon he saves a girl named Miyu and she falls in love with him. However, she cannot simply confess her love, and her twin sister Yumi decides to help her. But the more she helps her sister, the more she becomes confused in her own feelings...