Toshinori Yagi, known publicly as All Might, entered the world Quirkless amidst a society saturated with superhuman abilities called Quirks. He burned with an unwavering sense of justice even in youth, aspiring to become a symbol people could rely on in dark times. His mentor, Nana Shimura, the seventh user of the One For All Quirk, recognized his iron determination and selected him as her successor. She passed One For All to him before falling to the supervillain All For One. Toshinori then endured rigorous training under the pro hero Gran Torino, whose harsh methods forged his combat skills and mastery over One For All's immense power. Upon mastering the Quirk, Toshinori adopted the hero name All Might and the mantle of the Symbol of Peace. His iconic costume, frequently featuring red, white, blue, and gold, echoed classic American comic book heroism. Early in his career, he spent time in the United States, befriending scientist David Shield and naming signature "Smash" attacks like Detroit Smash and California Smash after American locales. All Might's overwhelming power, magnetic charisma, and relentless commitment to saving others with a smile slashed Japan's crime rate to 3-6% and ignited a generation of heroes. Roughly five years before the main events, All Might clashed catastrophically with All For One. Though victorious and forcing his nemesis into hiding, All For One inflicted a grievous wound that destroyed All Might's respiratory system and stomach, leaving a massive torso scar. This injury crippled his ability to wield One For All, restricting his powerful muscular form to just three hours daily initially, a duration that dwindled further. In his weakened state, he reverted to an emaciated, skeletal figure with sunken eyes, frequently coughing blood. He guarded this condition and true form fiercely to preserve public hope. Seeking a worthy heir, All Might encountered Quirkless teenager Izuku Midoriya. Witnessing Midoriya's innate heroism as the boy rushed to save classmate Katsuki Bakugo from a villain without powers, All Might recognized profound selflessness and grit. He chose Midoriya as the ninth user of One For All, initiating intense physical and mental training before passing the Quirk. To guide his successor closely, All Might accepted a Foundational Hero Studies teaching post at his alma mater, U.A. High School. Initially enthusiastic but pedagogically inexperienced, he relied on scripts and sometimes projected his own experiences onto Midoriya, causing early Quirk training hurdles. During the League of Villains' Kamino Ward assault, All Might battled All For One once more to rescue Bakugo. He expended the final embers of One For All to defeat his foe using the United States of Smash attack. This confrontation publicly exposed his frail form, ending his tenure as the Symbol of Peace. Though retired from active duty, he continued teaching at U.A. and mentoring Midoriya. Despite lacking his Quirk, he remained entangled in conflicts, including the Paranormal Liberation Front War and ensuing societal collapse. An encounter with the Hero Killer Stain challenged his self-view as a failure, reminding him of the enduring hope he still embodied. Determined to contribute in the Final War despite being Quirkless, All Might deployed the technologically advanced "Armored All Might" suit. Developed with Melissa Shield and integrated into his car, Hercules, the suit mimicked Quirks from Midoriya's classmates. He piloted it against All For One, adopting a tactical villainous persona during the fight. Though the armor was obliterated and All Might suffered crushed legs, Bakugo and Midoriya's intervention saved his life. The conflict altered him physically: his eyes regained white sclerae and his eyebrows became defined, though he initially required a wheelchair for recovery. Eight years post-war, All Might had regained mobility and served as U.A. High's vice principal. His appearance bore more wrinkles, yet retained the white sclerae and defined eyebrows acquired in his last battle, continuing his support for the next generation of heroes from this position.