As summer draws to a close, Shizuko's heart leapt when her family invited her to go to the beach on the day her husband returned from a business trip. However, her son Masaki struggled with a deep fear of water—he couldn't even submerge his face. Determined to help, Shizuko put on a new swimsuit and began intensive training with him, but Masaki's fear proved difficult to overcome. She then consulted Kunihiko, Masaki's childhood friend and a member of the school swim team, who offered advice that finally helped Masaki take his first steps into the water. As the bond between Shizuko and Masaki grows stronger, a story unfolds filled with the warmth and laughter of family—yet beneath the surface, forbidden desires begin to stir.