The narrative takes place in Minami Shimabara city, located in Nagasaki prefecture and known as the historic birthplace of the Shimabara Rebellion that reverberated throughout Japan during the early Edo period. Shirou, a third-year junior high school student, spends his days in this locale alongside his school comrades. During the summertime, Shirou's childhood friend Akane, who's currently living in Tokyo, returns to Minami Shimabara. Together with a long-time friend named Tokiya, Shirou and Akane stroll through the city, reminiscing and grappling with more nuanced emotions. Suddenly, their walk is interrupted by the arrival of Goron, an enigmatic little creature, triggering a series of life-changing events in the city.