After losing her husband, Chisato worked hard to support her family, working as an office lady by day and at an izakaya by night. Her daughter Aoi deeply admired her mother's strength and dedication, cherishing her more than anything. Over time, however, Aoi's feelings began to shift beyond simple familial love. One day, her younger brother planned a family trip using his first bonus and invited both women to join. But just before departure, he had to cancel due to an emergency. As a result, the journey proceeded with only mother and daughter traveling together—alone.