A financially struggling university student named Sanosuke Saraki takes a part-time job at his old high school. There, he unexpectedly reunites with Koharu Kobachi, a former classmate he once admired for being a genius in the sciences. However, he is shocked to discover that this brilliant girl has not advanced past high school and has been forced to repeat her final year multiple times, now a 20-year-old senior. Saraki is given a mission to live together with Koharu under the same roof and provide the support she needs to finally graduate within the year. The story follows their unusual domestic life as the young man attempts to help the brilliant but troubled girl overcome her personal obstacles and complete her education.