In elementary school, Kaiji and his younger identical twin brother Kyōji became engrossed in manga.[1] Kyōji took over running the Kawaguchi family business, but was also a manga artist before dying in 2013. Kaiji's daughter Nirako is an illustrator, while his eldest son Kōhei is aKanzenoh actor.[2] In 1968, Kaiji made his professional debut withYoru ga Aketara inYoung Comic at age 21, while still attendingMeiji University.[3][1]
Kawaguchi was influenced byShinji Nagashima, Tatsuhiko Yamagami'sHikaru Kaze, andTadao Tsuge. He also said that if it were not for the freedom and more adult material seen ingekiga, he probably would not have become a manga artist.[1] In seventh grade he became interested in cinematography after seeingAkira Kurosawa'sYojimbo. This early influence from film is still seen in his manganames, which are largely text and more like film screenplays, which he read for fun in high school, than the usual storyboards.[1]
In the middle of serializingHard & Loose (1983–87), Kawaguchi started drawing the eyes of his characters bigger. This was a suggestion by his editor, who told him that emotion is conveyed through the eyes. Before he made this switch, Kawaguchi said he never would have thought he would be able to draw Westerners and set his manga overseas.[1] The artist cited his work inActor (1984–88) as the basis for his current style.[1] Kawaguchi was a heavy smoker who insisted a cigarette was "indispensable" when drawing. However, after being treated foresophageal cancer in 2019, he quit smoking.[4]
