Katz Howan, later known as Katz Kobayashi after adoption, first appeared as a child refugee orphaned in the Zeon attack on Side 7 during the One Year War. Evacuated aboard the Federation warship White Base alongside Letz Cofan and Kikka Kitamoto, the trio became informal crew members despite objections, assisting with maintenance and critical tasks. They thwarted Char Aznable’s bomb plot at Jaburo by locating hidden explosives. After the White Base’s destruction at the Battle of A Baoa Qu, they demonstrated nascent Newtype abilities by psychically guiding Amuro Ray to their lifeboat. Adopted post-war by Hayato Kobayashi and Fraw Bow, Katz learned mobile suit piloting using vintage Zeon suits at Hayato’s museum. Inspired by Amuro’s actions, he developed a reckless, glory-seeking personality. During the Gryps Conflict, he aided Amuro in evading Federation surveillance and joined the anti-Titans group Karaba. In one skirmish, he saved Hayato’s forces by crashing a fighter into an enemy NRX-044 Asshimar, ejecting before impact. Transferring to AEUG space forces, his recklessness continued: he stole and crashed the RX-178 Gundam Mk-II during battle, requiring rescue. Despite disciplinary action, he persisted in unauthorized sorties, piloting the MSA-003 Nemo and later the G-Defenser. His judgment was compromised by infatuation with Titans officer Sarah Zabiarov. After her defection to AEUG, he facilitated her escape, resulting in his detention. He freed her again later but failed to prevent her return to the Titans. At the Gryps final battle, Katz piloted the G-Defenser supporting Emma Sheen against Yazan Gable. Disobeying withdrawal orders, he engaged Yazan directly. While evading attacks, he collided with a meteorite, lost consciousness, and was killed when Yazan destroyed his immobilized craft. His spirit appeared alongside Sarah’s, reassuring her they would stay together. In the "A New Translation" films, his death occurs identically, but his spiritual presence solely guides Sarah’s spirit instead of supporting Kamille Bidan.