27-year-old Arata Kaizaki, struggling with his stagnant life, is offered a chance to rejuvenate his youth through a mysterious experiment. Under the guise of a high school student, he must navigate the complexities of teenage life and forge new relationships while concealing his true identity. As he interacts with his classmates and confronts his own past, Arata begins to rediscover his own values and purpose.
Manga author Yayoiso is known to be from Oita and chose to model the school in the series off their own alma mater, Oita Uenogaoka High School. The whole main cast of the series has a name based off a JR station in Oita Prefecture. The ReLife drama movie is set at a different school.