Tokyo Heave-Ho Nina Iseri, a high school dropout who left Kumamoto, arrives in Kawasaki to prove her family she can live by herself. As the agency that rents the keys to her unit is closed for the night, Nina decides to stay at the station. While browsing social media, she sees a post of a street performance taking place within the area and runs towards it, encountering Momoka Kawaragi, a former member of a group Nina idolizes named Diamond Dust. Heading to Momoka’s house for Nina to stay, Momoka discloses she would be leaving Kawasaki the following morning to quit music, much to Nina's confusion...