"Chūsotsu Worker Kara Hajimeru Kōkō Seikatsu" centers on the life of Itsuki Tsuchiya, a 27-year-old man who, after failing to secure a stable career, works a series of part-time jobs to make ends meet. His life takes an unexpected turn when he is given the opportunity to relive his high school years through a mysterious program. The program allows him to enroll as a high school student once again, despite his adult age, under the condition that he must graduate within three years. Itsuki accepts the offer, hoping to correct the mistakes of his past and create a better future.

The narrative explores Itsuki’s struggles as he navigates the challenges of high school life while balancing his adult responsibilities and part-time work. His interactions with classmates, who are unaware of his true age, create a blend of comedic and heartfelt moments. Itsuki’s maturity and life experience often contrast with the naivety of his peers, leading to unique dynamics and misunderstandings. Key characters include Itsuki’s classmates, such as the diligent and kind-hearted Yuzuki Hoshino, who becomes a close friend, and the sharp-witted but aloof Rika Satō, who gradually warms up to Itsuki.

As the story progresses, Itsuki faces various personal and academic challenges, including confronting his own insecurities and regrets. The series delves into themes of self-improvement, second chances, and the importance of human connections. Itsuki’s journey is marked by moments of growth, as he learns to balance his dual identities and find meaning in his new life. The manga combines slice-of-life elements with lighthearted humor and occasional emotional depth, offering a reflective yet entertaining portrayal of Itsuki’s unconventional high school experience.