Kobayashi began drawing manga seriously during his university years, and won an honorable mention at the Weekly Shōnen Magazine's Rookie Award in 2000, allowing him to serialize School Rumble.
He stated to an audience at Honolulu's 2006 Kawaii Kon convention that he started writing the series because he found the idea of a manga involving a delinquent falling in love interesting.
[4][5] Most of the other characters are based on memories of former high-school classmates;[2] Kobayashi recalled that he had no real idea of their voices when drawing them, and it was not until much later, when he heard the voice actors' interpretations during the production of the anime series, that he knew how they should sound.
"[4] He claims that none of his stories are based on real-life events, although when pressed admits the possibility of some resemblances but without divulging specific details.
[7] He has made some cameo appearances in the anime adaptation School Rumble, supplying the voice of Sailor F in two episodes of the first season, and being the narrator of the prehistoric segment in the first OVA, School Rumble - First Term Extra.