Nezu is a genetically engineered chimera exhibiting traits from multiple animals—mouse, dog, and bear. His physical traits include white fur, a prominent scar across his right eye, black circular eyes, rectangular ears, an elongated muzzle, dog-like paws, and a thin tail. He typically dresses in formal attire: a white dress shirt, dark red tie, black double-breasted waistcoat, matching dress pants, and distinctive thick-soled orange sneakers. Years of human experimentation forged his background, triggering his Quirk "High Specs." This ability provides intelligence surpassing human limits, enabling abstract thought, complex problem-solving, and societal integration despite his non-human nature. Trauma from this period ingrained a lasting resentment toward humans, occasionally surfacing as sadistic behavior during combat or stress. As principal of U.A. High School, he prioritizes student safety and strategic oversight. Following All Might's retirement and attacks by the League of Villains, he transformed the school into a boarding facility (Heights Alliance) to closely monitor students while investigating a suspected traitor within U.A. This measure balanced security with cultivating hope amid societal instability. His security innovations encompass the U.A. Barrier for sealing unauthorized entry, plus post-war upgrades like mobile underground shelters, 3,000-layer bulwark defenses, and protocols to counter transformation-based infiltration by delaying entry to expose time-limited Quirks. Despite typically presenting as polite, eccentric, and deeply committed to education—often lecturing on pedagogy or advocating villain rehabilitation—his experimental past fuels a vengeful streak. This manifests as tactical cruelty in combat. During the Final Exams, he employed industrial machinery to collapse structures around students while laughing at their distress, demonstrating psychological manipulation and enjoyment of human vulnerability. His leadership emphasizes proactive crisis management. He sanctioned developing specialized combat techniques ("Ultimate Moves") for Class 1-A's Provisional License Exam preparation and joined strategic briefings after villain attacks. His operational philosophies include preserving public trust via discretion, exemplified by covering up students' unauthorized rescue mission to protect their futures while enforcing accountability. Beyond intellect, his abilities include enhanced senses like hearing and smell, proficiency in tea brewing, and industrial crane operation. In battle, he utilizes environmental manipulation and predictive strategies, such as herding opponents into inescapable traps through calculated destruction. Stat evaluations rate his intelligence as exceeding standard metrics (6/5 or S-rank), though his physical capabilities remain average. He maintains confidential relationships with staff, notably offering All Might a teaching position to safeguard him post-injury. His dialogues reflect on systemic heroism, including his belief that new symbols of peace must emerge to surpass All Might's legacy.