Katsuki Bakugo developed an early superiority complex from constant praise for his powerful Quirk and natural talents while growing up in Shizuoka Prefecture. His childhood friendship with Izuku Midoriya deteriorated into persistent bullying targeting Izuku's Quirkless status and heroism aspirations, stemming from Katsuki's insecurity about Izuku's inherently heroic mindset despite lacking powers. He manifested his "Explosion" Quirk around age four, combining his father's "Acid Sweat" and mother's glycerin secretion to create detonatable nitroglycerin-like sweat from his palms. Enrolling at U.A. High School intensified his rivalry with Izuku, especially after witnessing Izuku's newfound Quirk during the Quirk Apprehension Test. Early confrontations like the Battle Trial revealed Katsuki's shock at Izuku's capabilities and his refusal to acknowledge their shared admiration for All Might. His aggressive demeanor and poor teamwork caused failures including losing the Battle Trial and Provisional Hero License Exam. A turning point occurred during his kidnapping by the League of Villains. His rescue led to All Might's retirement, fueling intense guilt and self-blame that catalyzed introspection. This culminated in a clandestine battle where Katsuki deduced the truth of One For All, leading to a truce and the start of a respectful yet combative rivalry. Throughout U.A., Katsuki honed combat strategies and Quirk applications. Key techniques included concentrated explosive blasts ("AP Shot"), spinning aerial detonations ("Howitzer Impact"), and blinding flashes ("Stun Grenade"). Support gear like "Grenadier Bracers" stored sweat for larger explosions, while "Strafe Panzer" shoulder cannons enhanced firepower during the Final War. His internship with Best Jeanist forcibly altered his appearance—combing his spiky hair and modifying his costume—though he retained core elements: a black tank top with an orange "X," grenade-themed gauntlets, and tactical knee pads. Stealth missions like Operation: Humarise required specialized neoprene suits with streamlined bracers. Character development accelerated through collaboration. The Remedial Course Arc saw him advising a child against arrogance, reflecting growing self-awareness. During the Paranormal Liberation War, he instinctively shielded Izuku from a fatal attack, awakening the explosive propulsion technique "Cluster" and symbolizing his shift toward valuing others' lives. His evolution peaked in the Dark Hero Arc with a tearful apology to Izuku, admitting past bullying stemmed from jealousy of Izuku's innate heroism and explicitly validating Izuku's worthiness to inherit One For All. In the Final War, Katsuki sacrificed himself to protect All Might, sustaining a fatal chest wound from Tomura Shigaraki. Edgeshot's "Zenith" technique revived him, leaving prominent scars on his right arm, cheek, and torso. Despite severe injuries, he rejoined the battle using All Might's armored suit splint for his shattered arm. His strategic intervention prevented Kurogiri from teleporting Shigaraki away, enabling Izuku's victory. Post-graduation, he ranked among Japan's top heroes and funded advanced support gear for Izuku. Eight years later, as the No. 5 Pro Hero "Dynamight," he displayed taller, leaner musculature, braided hair resembling fuses, and streamlined smoke-grenade gauntlets. His costume retained signature elements while incorporating long sleeves to conceal war scars. OVAs and movies contextualized his growth. In *Heroes Rising*, he temporarily wielded One For All alongside Izuku to defeat Nine, demonstrating unprecedented cooperation. *World Heroes' Mission* featured him in a tactical stealth role against Humarise during the Otheon mission. Training OVAs like "Make It! Do-or-Die Survival Training" highlighted his competitive drive in non-canon scenarios. Katsuki's personality evolved from crude arrogance to disciplined intensity. He retained trademark yelling, competitiveness, and blunt honesty but integrated respect for allies like Eijiro Kirishima and Shoto Todoroki. His strategic intellect—evident in academic rankings and battlefield improvisation—complemented his combat prowess. Despite maintaining insulting nicknames, he gradually accepted teamwork and leadership roles, driven by an uncompromising pursuit of victory and self-improvement.