Kawadzu Sakura is an office worker who is neither enthusiastic nor challenging, but does not have the courage to change jobs. One day after working overtime, she happens to enter a public bathhouse sauna and meets a cool coworker, Somei Yoshino. They had never talked much, but Somei, who wanted to make a sauna friend, taught Kawadzu how to enjoy the sauna. Kawadzu and Somei were so fascinated by the sauna that they began to visit saunas together. Then Kawadzu's grandmother, who runs a bathhouse by herself, collapses…!?