Yuu Watanabe, a 30-year-old corporate employee, traveled back to the age of 17 due to an accident and became a student at a high school in Tokyo. Faced with a completely different life, he had to find a balance between schoolwork, part-time work and adolescent social life. He met the mysterious netizen Ayano Amamiya through anonymous writing on the Internet, and the two shared loneliness and ideals in the virtual world; in reality, he and Yuki Hayakawa secretly fell in love because of the joint planning of the campus festival, and were involved in a more complicated relationship because of helping his neighbor Ryoko Hamabe take care of her sick grandmother. In the end, Yuu Watanabe gradually understood through academic progress, emotional choices and self-worth realization that true growth is not only about reliving youth, but also about facing the regrets and responsibilities that cannot be avoided in every stage of life.