Chin Kyuu originates from China's Three Kingdoms period as the historical strategist Chen Gong, forcibly displaced into modern Japan. Now inhabiting an elementary school student's body alongside Ryofu Housen, he retains his adult memories despite his youthful appearance, marked by distinctive glasses and a hat. His personality merges ancient traits with his current child form, manifesting as a relentless obsession with adult themes—particularly a fixation on women's bodies and tactile encounters with Eri-sensei's breasts, driving frequent comedic scenarios.

Throughout the narrative, Chin Kyuu faces obstacles with Ryofu, including clashes with resurrected Three Kingdoms rivals and absurd modern threats like epic monster battles. He consistently initiates or engages in inappropriate behavior fueled by perverted tendencies, leveraging his childlike guise for adult-oriented humor and ecchi elements. No character evolution occurs; Chin Kyuu remains statically defined by the contrast between his elementary school aesthetics and overtly sexualized motivations. His role exclusively supports comedic interactions without advancing personal growth or storyline resolution.