Eijirō Kirishima harnesses the "Hardening" Quirk, letting him solidify and sharpen any body part into jagged, rock-like armor resistant to bullets, explosions, and impacts. This durability has limits; excessive damage weakens or shatters it. Rigorous training birthed techniques like "Red Riot Unbreakable," achieving near-indestructibility briefly at significant cost. His combat style emphasizes defense and direct clashes, using his hardened form to shield allies and strike back. Kirishima champions bravery, chivalry, and self-improvement, frequently praising courageous acts as "manly." Outgoing and encouraging, he values loyalty intensely, forging a rare mutual-respect bond with Katsuki Bakugo. Despite his energetic front, Kirishima battles lingering self-doubt stemming from a middle school failure to stop an underclassman's bullying, leaving him feeling cowardly. An interview featuring his idol, the retro hero Crimson Riot, changed this; Crimson Riot's words about heroism inspired Kirishima's transformation. He dyed his hair red and spiked it, symbolizing his commitment to live without regret. This drive fueled intense training, securing his place at U.A. High. During the "Do-or-Die Survival Training," Kirishima served in Team A with Bakugo and Denki Kaminari, tasked with rescuing a training dummy from a collapsing, flooded mall. He shielded Kaminari from debris with his Quirk. When Bakugo prioritized finding the dummy despite danger, Kirishima backed him, insisting true heroes save others regardless. After locating the dummy pinned under rubble, Kirishima collaborated with Bakugo and Kaminari to free it, tempering Bakugo's aggression with caution to prevent further collapses. He later helped carry the dummy to safety through rising floodwaters, prioritizing team success. Kirishima's growth continued. His Work-Studies under Fat Gum tested his resolve, particularly during the Shie Hassaikai raid where he endured Kendo Rappa's blows to protect others, cementing his reputation for unyielding spirit. Kirishima graduated U.A. and became the Pro Hero "Red Riot," ranked No. 12 nationally. His journey—from a self-doubting youth to a top hero—embodies his core belief: true strength is facing fear without regret.