Konta, once a promising swimmer, saved a girl from drowning in the sea. Although her life was barely spared, she remained in a coma, and Konta quit swimming out of a sense of self-reproach. Five years later, Konta has become a shut-in (Hikikomori), a shadow of his former self. Unable to stand by and watch his plight, his older sister invites him to become a coach for the elite Shikinomori High School swimming club. Reluctantly heading to the pool, he encounters the very girl he saved all those years ago—. Now, the curtain rises on a new story of youth and girls' sports!