Kaname Okiura, a student at Prefectoral Umineko Shougyou High, joins the school’s swimming club simply to learn how to swim. The club, however, is populated by a cast of eccentric members and lacks any proper instruction. When a bright‑spirit, happy‑go‑lucky girl named Amuro Ninagawa transfers from Okinawa and also joins the club, she quickly captures everyone's attention. Amuro is known for her extraordinary underwater speed and unorthodox swimming style, and her habit of swimming nude becomes an irresistible magnet for teenage boys. Okiura is especially taken by her, as she evokes the memory of a mermaid‑like creature he once saw in his childhood.
