Kaijuu no Kodomo

During a summer break, Ruka encounters two boys named Umi and Sora, who possess mysterious and intriguing backgrounds. Fascinated by their graceful swimming, which resembles flying, Ruka and the adults familiar with them become entangled in a complicated situation. At the same time, a puzzling global phenomenon is taking place: fish are vanishing from the oceans. This sets the stage for a sea-based journey involving the boys and girls, designed to engage all the senses.