tonari no seki-kun
A 2010 slice-of-life comedy manga by artist Morishige Takuma later adapted into an anime in 2014. It features Seki Toshinari who is an eccentric highschool boy passes time coming up with strange games, jokes, pranks and the like to entertain himself during class, and Yokoi Rumi, his female classmate, who sits at the desk next to him and reacts to his antics and attempts to reign him in.
The manga has a 2020 spin-off called Tonari no Seki-kun Junior in which Rumi has grown up and had a child and engages in similar antics with her son (who's father is implied to likely be Seki).