A prodigy of science and a solitary genius—but with plenty of weaknesses!? Struggling university student Sanosuke Saragi unexpectedly reunites with his high school crush, the brilliant classmate Koharu Kobachi, while working part-time at his old school. But to his shock, the "genius" girl is now a two-time repeater… a "5th-year high schooler." Sanosuke is assigned one mission: "Make sure Koharu graduates this year." Thus begins a bittersweet youth story of second chances, as a 20-year-old high schooler and her old classmate live under the same roof!