Arata Kaizaki is an unemployed, single 27-year-old who has just been cut off from his parents' financial support. Unable to find a job due to him leaving his previous employer within three months, he is stuck. One night after drinking with a high school friend, Arata meets Ryō Yoake, a man who offers Arata pills to turn him back into a 17-year old so he can redo his life. After agreeing to the experiment, Arata joins a high school class, and meets Chizuru Hishiro, a socially-awkward silent beauty who yearns to have friends. Through connecting with her and other classmates, Arata must find what he lacks to live a happy life in the real world within a one-year time limit.