Naomasa Tsukauchi, a police detective renowned for sharp analytical prowess and unwavering dedication to justice, grew up as the eldest son of the Tsukauchi family. His younger sister Makoto’s childhood development of a Polygraph Quirk, which frequently tested his honesty, sparked intermittent sibling clashes. These early experiences with Quirk-driven interpersonal dynamics steered his career toward law enforcement, where he focused on Quirk-related crimes. Specializing in Trigger-related investigations after joining the police force, he frequently crossed paths with vigilantes like the Naruhata group. Though acknowledging their effectiveness against Instant Villains, he openly criticized their disregard for legal protocols, advocating instead for strict adherence to lawful heroism. His professional trajectory intertwined with Pro Heroes, most notably All Might. Discovering the symbol of peace in a weakened state forged a confidential alliance, with Naomasa providing logistical support and discretion. Together, they coordinated high-stakes operations, from Katsuki Bakugo’s rescue to tracking Tomura Shigaraki and Kurogiri. In the spin-off series Vigilantes, Naomasa pursued Trigger distribution rings and the Villain Factory, an entity augmenting villains’ resistance to the drug. This investigation unexpectedly reunited him with Makoto, who covertly oversaw the vigilante Pop☆Step. Despite clashing over her vigilante ties, he shielded her during the Tokyo Sky Egg crisis, prioritizing her safety over ideological differences. Physical changes mirrored his career’s toll: post-Paranormal Liberation War stress manifested in a light goatee and pronounced eye bags, later replaced by a clean-shaven but fatigued demeanor after the Final War. Though never confirmed, his aptitude for truth detection—hinted as a familial trait akin to Makoto’s Quirk—complemented his investigative strengths in pattern analysis, strategic foresight, and composed crisis management. Pragmatism occasionally led him to ally with vigilantes like Koichi Haimawari when circumstances demanded. A baseball enthusiast, his name symbolizing honesty, Naomasa’s journey reflects a tension between uncompromising professionalism and measured empathy, particularly when navigating moral gray areas or potential redemption cases. His evolution underscores the challenges of upholding justice in a society grappling with instability and ethical complexity.