Fifteen years ago, Emiko divorced and raised her son, Tatsuya, all by herself. Wanting to spare him hardship as a single mother, Emiko worked tirelessly to support them. Thanks to her dedication, Tatsuya successfully graduated from college and started working at a beverage company, living a modest yet happy life. One day, Emiko began complaining of physical discomfort. Realizing she had been overexerting herself for his sake, Tatsuya invited her to a hot spring resort to help her relax.