Hisui was happy living her life on Kohaku Island, where she learned to love the sea and the animals there. However, her family moves and she has to leave her old life behind, including her dear dolphin friend Kairi. At her new school, she's seen as a bit of an oddball thanks to her love for swimming; however, when she meets Minato, star of the swim team, they hit it off. Minato reminds Hisui of Kairi, but there might be something more than that in her affection for him.