Fifteen years ago, Kaede divorced and raised her son Hiroaki all by herself. Worried about his future, she worked tirelessly to support him through college. Hiroaki landed a job at a beverage company, and the two were living a modest yet happy life together. However, when Kaede fell ill, Hiroaki realized she had been overexerting herself solely for his sake. Wanting her to relax, he invited her on a hot spring trip, hoping to ease her burdens.