A few years after marrying her husband, married woman Yuu has been troubled by the mismatch between her and her husband, who is busy working night shifts. Night shifts are apparently very physically demanding, and they haven't had sex at night for the past three years. One day, a part-time coworker suggested she take swimming lessons to change her mood. When she talked to her husband about it, he didn't seem interested, which made Yuu feel even more lonely. With these thoughts in mind, Yuu started attending swimming lessons, and gradually became attracted to the honest Kokoro and muscular body of the young instructor, Hosoda...