Umi Monogatari

Marin and Urin are sea-dwelling people who live in a tranquil underwater world, filled with vibrant fish and coral. One day, a beautiful ring drops from the "sky"-the perilous world above the water-and the two girls resolve to return it to its owner. Their journey to the surface reveals breathtaking wonders, but it also awakens a hidden darkness when Urin accidentally opens a mysterious stone box at a shrine. Now Marin, Urin, and their new friend Kanon must undo the chaos before the darkness consumes everything.