Description:

A prodigy of science and a solitary genius—yet terrible at so many things!? When the poor university student Sanosuke Saraki started at a new part-time job at his old high school, he unexpectedly reunites with Koharu Kobachi, a classmate that he admired as a brilliant genius. However, this supposed genius is now a "5th year high school student" who must repeat her senior year for the second time…! Saraki's mission is to "help Koharu graduate by the end of the year." A coming-of-age story about starting over with a 20-year-old high school student! (Source: AniList)

Alternative Titles:

屋根の下のアルテミス, Artemis Under the Roof