Zenitsu Agatsuma is a Demon Slayer whose cowardly, anxiety-ridden exterior masks fierce capabilities. He frequently anticipates his own death due to his perilous profession and exhibits low self-esteem, deeming himself useless despite his skills. His instinct to flee threatening situations stems from a desire for a normal life, influenced by his orphaned background and a past swindling by a woman he loved, which plunged him into debt. Former Thunder Hashira Jigoro Kuwajima rescued him, settling his debts and training him in swordsmanship alongside Kaigaku—a fellow disciple with whom Zenitsu shared a contentious relationship. During training, a lightning strike permanently altered Zenitsu's hair from black to yellow. Zenitsu persistently pursues marriage proposals to attractive women, driven by comedic desperation to avoid dying single. This contrasts his genuine loyalty: he fiercely protects Nezuko Kamado and deeply reveres Jigoro. Extreme fear triggers unconsciousness, shifting him into an alternate combat state where he fights with calm precision and accesses his full potential. Jigoro’s suicide—prompted by Kaigaku’s demon transformation—hardens Zenitsu’s resolve, culminating in focused determination during later conflicts. His combat style centers on Thunder Breathing; initially mastering only the first form, Thunderclap and Flash, he later refines it into high-speed variations like Sixfold, Eightfold, and Godspeed. Zenitsu’s heightened hearing detects subtle sounds, including emotions, heartbeats, and demon presence. While unconscious, he executes techniques with impeccable judgment and reflexes. He eventually creates an original seventh form, Flaming Thunder God, manifesting as a lightning dragon to defeat Upper Rank Six demon Kaigaku. His physical prowess includes speed surpassing Upper Ranks, leg strength enabling explosive leaps, and endurance to fight through broken bones or poison. Physically, Zenitsu has fair skin, gold-fading-to-brown worried eyes, and yellow hair with orange tips. He wears a pale brown Demon Slayer uniform and a white-triangle-patterned yellow-to-orange haori. Son’s poison temporarily shrunk his limbs after Natagumo Mountain until Shinobu Kocho’s antidote reversed it. Key relationships shape his journey: Tanjiro Kamado acts as a grounding friend; Inosuke Hashibira engages in clashes yet mutual reliance; Nezuko inspires his protectiveness; Jigoro embodies paternal respect and growth motivation; Kaigaku represents betrayal, fueling their final confrontation. Zenitsu evolves from unconscious combat reliance to conscious courage, contributing decisively in battles against Muzan Kibutsuji.