A 17-year-old high school student named Nina Iseri from Kumamoto makes a drastic decision after a painful experience. She had stood up for a bullied classmate, only to become a target herself, with the school and even her parents pressuring her to compromise for the sake of her academic future. Feeling utterly betrayed by a world that refuses to admit she was in the right, Nina withdraws from school and flees to Tokyo.

Her destination is not the neon-lit center of the capital but the industrial city of Kawasaki. After a series of mishaps leaves her stranded, Nina has a chance encounter with Momoka Kawaragi, a street musician whose former band, Diamond Dust, was Nina's only source of solace during her lonely high school days. Momoka, having recently quit Diamond Dust due to creative differences with their management, is on the verge of giving up on music and moving back to her hometown. Nina's fierce, unyielding spirit and powerful voice reignite Momoka's passion, convincing her to stay in Kawasaki and form a new band.

They soon recruit the charismatic Anon Subaru, a talented drummer from a famous acting family who is secretly rebelling against the predetermined path set by her beloved grandmother. Later, they join forces with two other musicians: the precise and blunt keyboardist Tomo Ebizuka and the calm, motherly bassist Rupa, who have their own history of struggles in the music industry. Together, they form the band Togenashi Togeari.

The central conflict of the story arises from Nina's refusal to back down. Her primary motivation is to prove that she was never wrong, a sentiment she channels into a fierce rivalry with the new incarnation of Diamond Dust, which has transformed into a popular idol-like band. The situation is complicated by the discovery that the new lead vocalist of Diamond Dust is Hina, Nina's former friend from Kumamoto who took the side of the school and the bullies. This rivalry puts immense pressure on the band, particularly on Momoka, who carries guilt and trauma from her own departure from Diamond Dust. Key narrative arcs include a concert where Togenashi Togeari must prove their worth against their rivals, a deeply emotional episode where Nina returns home to confront her parents and find resolution with her family, and the band's difficult decision to reject a commercial deal that would force them to compromise their artistic integrity for fame.