Kuchiki shows up in volume two and officially joins Genshiken in volume four, apparently after getting booted from the Anime Club. He's loud, abrasive, and has no filter—he'll happily spy on girls or do whatever else amuses him without much shame. Before Genshiken, he was already part of the Anime Society, and he's totally fine with cosplay despite his rough demeanor. He wants people to call him Kuchi and actually enjoys it when they do.
Gaming-wise, he's legitimately skilled at fighting games, second only to Kousaka in the group. That said, he's mostly around for comedy. He functions as the straight man's punching bag, taking the brunt of Genshiken's slapstick humor and crude jokes. He's even expected to become president twice, only to get passed over by Ohno and then Ogiue—which probably stings more than he'd admit.
In the manga relaunch, it turns out Kuchiki doesn't actually need to stress about his future. Family connections have basically guaranteed him a job at a local bank, so he's set regardless of whatever else happens with the group.
Content compiled by AnimeList.moe from publicly available sources.