Orphaned during the Zeon attack on Side 7 at the One Year War's outset, Katz Hawin evacuated aboard the Earth Federation vessel *White Base*. Alongside fellow orphans Letz Cofan and Kikka Kitamoto, he overcame initial resistance to assist the crew, participating in critical events like Ramba Ral's final attack and aiding in the disposal of bombs planted during Char Aznable's infiltration of Jaburo, actions solidifying their place aboard. During the Battle of A Baoa Qu, Katz, Letz, and Kikka exhibited nascent Newtype abilities, psychically guiding Amuro Ray to the crew's escape lifeboat. Adopted post-war by Hayato Kobayashi and Fraw Bow, taking the surname Kobayashi, Katz honed piloting skills operating Zeon mobile suits at Hayato's museum. This fostered a reckless, headstrong personality fueled by idolizing Amuro's exploits. By the Gryps Conflict, Katz actively sought military service, defying Fraw's concerns. He aided Amuro in evading Earth Federation surveillance and joined the anti-Titans group Karaba. During a Karaba operation, he rescued Hayato's forces by crashing a fighter into an enemy mobile suit, bailing out safely before impact. Impulsiveness led him to stow away in the RX-178 Gundam Mk-II during a skirmish, crashing it into water. Rescued by AEUG pilots, he later damaged Rosamia Badam's Gaplant, contributing to its destruction, though Hayato reprimanded him. Transferred to the AEUG spaceship *Argama*, Katz trained as an MSA-003 Nemo pilot. He became infatuated with Titans defector Sarah Zabiarov, leading to manipulation; he facilitated her escape back to the Titans after she fed him false intelligence about a colony drop, resulting in his detention. Reassigned to the *Radish*, Katz disobeyed orders again, piloting the G-Defenser to support Emma Sheen against Yazan Gable. His intervention enabled Emma to deploy the Super Gundam, but Yazan pursued him. Stranded on a derelict ship, Katz used a damaged Gelgoog to distract Yazan, saving Kamille Bidan. These actions earned him a pardon and appointment as the G-Defenser's official pilot. Later, during the Gate of Zedan battle, he sensed Sarah's presence and intervened to save Kamille from Jerid Messa, cuffing Sarah upon their return. Katz's fixation on Sarah persisted, causing neglected duties and obsessive monitoring of her captivity. He pursued her when she escaped again but hesitated to shoot despite Emma's backup. During the final Gryps Conflict battles, he blamed Haman Karn for Sarah's death and attacked her against orders, requiring Fa Yuiry's intervention to disengage. Supporting Emma against Yazan in the conflict's climax, Katz ignored retreat orders. Evading Yazan's attack, he crashed into a meteorite, lost consciousness, and died when Yazan destroyed his crippled G-Defenser. His spirit united with Sarah's in death. Posthumously, his death resonated psychically with AEUG members, his spirit manifesting to aid Emma Sheen during her duel with Yazan. He appeared among the fallen spirits guiding Kamille Bidan in the final assault against Paptimus Scirocco. During the First Neo Zeon War, his spirit briefly protected Judau Ashta from Haman Karn at Axis. In the *A New Translation* film version, his death scene omitted the meteorite collision; his spirit appeared to Sarah but did not join Kamille's spectral allies.