In the opening episode, young lovers Mizuho and Hiro decide to enhance her fitness through swimming lessons. Hiro, working at the local pool, offers private coaching sessions after hours to help her improve her strokes. What starts as a simple exercise routine quickly becomes an intimate adventure filled with splashing water and close encounters in revealing swimwear. At the same time, Takuya encounters an unexpected moment with his charming neighbor Sayaka, leading to a playful situation involving wet attire and shared discoveries.