Eijiro Kirishima trains to become a professional hero at U.A. High School under the alias Red Riot, inspired by his idol, the retro hero Crimson Riot. His appearance features spiky red hair, dyed and styled upward with gel – a transformation from his original black, shoulder-length hair in middle school symbolizing his commitment to Crimson Riot's ideals of courage and resilience. He possesses a muscular physique, red eyes, and a small scar above his right eye. His hero costume includes dark red gear-shaped shoulder pads, a jagged sash with a red "R," black pants, a ripped half-cape, and a wired face guard resembling an oni, later modified with black sleeves to prevent civilian injury during rescues. Born in Chiba Prefecture, Kirishima manifested his Quirk, Hardening, at age three, accidentally cutting his eye during its first use and resulting in his scar. Initially disliking his Quirk for causing pain, he later admired Crimson Riot, whose similar abilities and philosophy emphasizing bravery over Quirk reliance reshaped his outlook. While attending Mustafa Private Middle School alongside Mina Ashido, an incident where he failed to intervene against bullies or protect peers, unlike Mina, fueled his insecurities about his perceived inadequacy as a hero candidate. After nearly abandoning his U.A. aspirations, he rediscovered resolve through a holographic interview of Crimson Riot discussing fear and regret. Kirishima dedicated himself to rigorous training and study, later apologizing to those he couldn't protect and reinventing himself upon entering U.A. Kirishima's personality centers on chivalry, resilience, and a personal code of "manliness," defined as living without regret through bravery, honesty, and protecting others. He openly admires acts of determination, often moved to tears, and rejects cowardice or underhanded tactics. Despite his outgoing and encouraging demeanor, he battles self-doubt regarding his Quirk's perceived lack of flashiness, fearing it may limit his hero potential, an insecurity stemming from middle school that drives relentless self-improvement. He is exceptionally loyal, willing to break rules to aid friends, and harshly self-critical when unable to assist others. His perseverance earned him the self-declared title "a horse that never wavers" during a high-stakes internship battle. His abilities include above-average natural durability amplified by his Hardening Quirk, allowing him to harden and sharpen his body into rock-like armor, rendering him bulletproof and explosion-resistant, though prolonged damage weakens the effect. His fighting style combines defensive shielding with aggressive counters, leveraging enhanced strength to smash opponents. Key techniques are Red Counter, enduring attacks to deliver close-range strikes, and Red Riot Unbreakable, his ultimate move pushing Hardening to its limit for 30–40 seconds, transforming his body into a near-indestructible, monstrous form. This move proved pivotal during the Shie Hassaikai raid, where he withstood Kendo Rappa's barrage to protect Fat Gum. Academically, Kirishima ranked second in the U.A. Entrance Exam through combat and rescue points and eighth in the Quirk Apprehension Test. He fought low-tier League of Villains members during the U.S.J. incident and tied with Tetsutetsu Tetsutetsu in the Sports Festival due to their identical Quirks and styles. His internship under Fat Gum honed his skills, leading to victories against Trigger-enhanced villains and contributions during the Shie Hassaikai operation. In joint training battles, his collaboration with Koji Koda pressured opponents like Jurota Shishida, who acknowledged Kirishima as a significant threat. Kirishima's relationships are defined by mutual respect and growth. His bond with Katsuki Bakugo is particularly notable; Bakugo considers him an equal, and Kirishima's unwavering support during the Hideout Raid to rescue Bakugo solidified their rivalry-friendship. He maintains camaraderie with Mina Ashido, who knew him pre-transformation, and mentors under Fat Gum, who praised his spirit. Within Class 1-A's "Bakusquad," including Denki Kaminari and Hanta Sero, Kirishima acts as social glue, diffusing tensions and fostering teamwork. Eight years after the Final War, Kirishima graduated from U.A. and became the No. 12 Pro Hero. His physique grew bulkier, his hair longer and spikier, and his hero costume remained largely unchanged. This rank reflects his fulfillment of Crimson Riot's legacy.