Zenitsu Agatsuma, a Demon Slayer marked by the clash between his trembling anxiety and lethal mastery of Thunder Breathing, evolves from a cowering recruit into a resolute warrior through relentless trials. Mentored by retired Thunder Hashira Jigoro Kuwajima, he initially stagnates at the First Form, his frustration deepening amid rivalry with senior disciple Kaigaku, who masters all techniques except the one Zenitsu perfects. The Infinity Castle arc thrusts Zenitsu against Kaigaku, now Upper Rank Six, unraveling their fractured past. Jigoro’s suicide—sparked by shame over Kaigaku’s demonic turn—fuels Zenitsu’s vow to honor their master. In their duel, he unveils Thunder Breathing’s self-crafted Seventh Form: Honoikazuchi no Kami, a lightning-charged strike blending speed and surgical precision. This innovation mirrors his ascent from reliance on a single technique to forging his own path, cementing his maturity. Zenitsu’s combat prowess peaks in unconscious states, where fear dissolves into hyper-focused agility. His signature Thunderclap and Flash cleaves foes in a blinding rush. Despite paralyzing terror when conscious, he repeatedly risks his life for allies like Tanjiro and Inosuke, loyalty trumping self-preservation. Key missions, including the Mugen Train operation with Kyojuro Rengoku, test his mettle against threats like Lower Rank One Enmu and Upper Rank Three Akaza. Though overshadowed by Rengoku’s leadership, Zenitsu proves indispensable in the fray. Abandoned by debt-ridden parents and rescued by Jigoro, his insecurities duel with a desperate need to prove worth. His unwavering compassion surfaces in gentle admiration for Nezuko Kamado, even in her demon form. Post-battle collapses often leave him dependent on allies like Murata for recovery. A dream encounter with Jigoro, who names him his "pride and joy," crowns his journey from insecure apprentice to honored slayer. Zenitsu’s narrative arcs from comic timidity to tempered resolve, balancing levity with visceral courage. His growth, etched through perseverance, self-acceptance, and Jigoro’s mentorship, anchors him as a cornerstone of the saga.