Manabu Kuchiki, who prefers the nickname "Kucchi," joined the Genshiken club alongside Chika Ogiue in volume four of the manga after expulsion from the Anime Club. He is tall with a short haircut, a long oblong-shaped face, and frequently speaks with pursed lips while making awkward poses. His personality is loud, obnoxious, and hyperactive, often offending others through a lack of personal space and inappropriate behavior like spying on female members and attempting sexual assaults, which frequently results in physical retaliation from the club. He openly imitates anime character voices and movements, contributing to his socially abrasive demeanor. Despite this, he occasionally displays good intentions, such as helping catch a thief by annoying them into returning stolen goods during a school fair and protecting Hato’s secret identity by creating a diversion that led to him being choked—an act he enjoyed.

As an otaku, Kuchiki specializes in an expansive "cute-fixation" fandom, adoring anything he deems charming and frequently using the "-chan" honorific. He is an enthusiastic cosplayer, including cross-dressing, and exhibits no shame in these activities. He is also the second-best fighting game player in Genshiken, surpassed only by Makoto Kousaka. Kuchiki twice expected to become Genshiken president but was overlooked in favor of Kanako Ohno and later Ogiue. His role within the club is primarily comedic, serving as the "boke" (fool) to the other members' "tsukkomi" (straight man) in slapstick scenarios. Professionally, he does not need to seek employment due to a guaranteed banking job secured through family connections. His character development remains minimal across the series, maintaining his role as a source of off-color humor and occasional unexpected assistance, while his core traits of social obliviousness and hyperactivity persist.