Marin and her younger sister Urin are seafolk who happen upon something quite strange: a beautiful silver ring lost beneath the waves. The kind-hearted Marin, intent on returning it to its owner, drags a reluctant Urin along with her to the sky world despite reminders of a turtle elder who left for the surface and never returned. After locating the ring's owner, Kanon Miyamori, they learn that Kanon had tossed it int...