Zenitsu Agatsuma serves as a Demon Slayer Corps member alongside Tanjiro Kamado. He possesses fair skin, downward-sloping eyes fading from brown to gold, and short yellow hair transitioning to dark orange at the ends, a change from his original black hair caused by a lightning strike during training. His attire consists of a pale brown Demon Slayer uniform and a yellow-to-orange gradient haori patterned with white triangles. Orphaned young, Zenitsu incurred debt after being swindled by a woman he admired. Former Thunder Hashira Jigoro Kuwajima rescued, adopted, and trained him in Thunder Breathing. Zenitsu frequently attempted to escape training and struggled to master beyond the style's first form. His peer Kaigaku openly criticized his cowardice and informal demeanor, fostering a lasting rivalry. The lightning strike altering his hair occurred while he hid from Jigoro during a storm. Zenitsu exhibits extreme cowardice, low self-esteem, and constant anxiety, convinced his role will lead to an early death. He frequently begs women to marry him, fearing he will die alone, leading to an immediate infatuation with Nezuko Kamado whom he vows to protect. Despite his fears, he demonstrates loyalty, such as defending Nezuko's box from Inosuke Hashibira despite knowing it contained a demon. When unconscious due to terror, his personality shifts dramatically: he becomes calm, analytical, and combat-proficient, accessing his full abilities without hesitation. Over time, he learns to fight while awake, particularly after learning Jigoro died by suicide—a result of Kaigaku's demon transformation and betrayal. This event hardens Zenitsu’s resolve, leading to a more focused and mature demeanor. Zenitsu possesses exceptionally acute hearing, enabling him to detect subtle sounds, identify emotions, locate demons, and predict movements. His combat prowess centers on Thunder Breathing, though he initially mastered only the First Form: Thunderclap and Flash. He honed this technique to perform successive strikes—Sixfold and Eightfold variations—and developed Godspeed, a high-speed variant usable twice daily before leg strain. During the battle against Kaigaku, now Upper Rank Six, Zenitsu created the seventh form: Honoikazuchi no Kami, manifesting as a lightning dragon for a decapitating strike. His physical abilities include immense speed (outpacing Upper Rank demons), leg strength for high jumps, and endurance to fight through severe injuries and poisons. He shares a brotherly bond with Tanjiro, initially resenting him but growing to respect his kindness. His dynamic with Inosuke involves constant squabbling yet mutual reliance in battle. Zenitsu’s devotion to Nezuko motivates protective actions, including confronting the Upper Rank demon Daki to save a human girl. His relationship with Jigoro was foundational; though Zenitsu avoided training, he deeply respected his master and carried his legacy. The discovery of Kaigaku’s betrayal and Jigoro’s subsequent death became a pivotal motivator, leading Zenitsu to confront and defeat Kaigaku independently.