Kento Nanami studied at Tokyo Jujutsu High, forging a close bond with classmate Yu Haibara. As first-years, they trained under second-year mentors Satoru Gojo and Suguru Geto, undertaking perilous missions such as the Star Plasma Vessel escort. Witnessing the jujutsu world's brutality, especially Haibara's mission death, deeply disillusioned Nanami. He deemed the profession demanded unacceptable sacrifice, leading him to abandon sorcery after graduation for a corporate career. Working as a salaryman in securities, Nanami endured grinding pressure and ethical compromises he found equally hollow. He described this life as purposeless, his labor merely enriching the wealthy without meaningful contribution. A turning point came exorcising a low-grade curse afflicting a bakery worker; her unexpectedly heartfelt thanks made him recognize the value of protecting others. This prompted his return to jujutsu, adopting a philosophy: since both paths were "crap," he chose the one where his aptitude allowed him to accumulate small appreciations from those he saved. Nanami possessed a tall (184 cm), well-built frame. His blonde hair was precisely parted in a 7:3 ratio, complemented by thin eyebrows. Small hazel eyes were typically shielded by distinct armless sunglasses. He dressed in formal business attire reflecting his corporate past: a blue dress shirt, tan blazer, dotted-pattern tie, and matching slacks. A holster beneath his blazer concealed his blunt sword, its bandages matching the tie's dotted pattern. During the Shibuya Incident, he sustained grave injuries: Dagon claimed his left eye, while Jogo inflicted extensive burns on his left side, scorching half his hair and flesh. Personality-wise, Nanami was reserved, stoic, and pragmatic, his calm demeanor often appearing aloof. He strictly separated sentiment from duty, openly expressing irritation and disliking inefficiency, abstract questions, or overtime—ending his workday rigidly at 6:00 PM. Underneath, he valued intelligent conversation and displayed a dry wit, labeling sorcery "slightly less idiotic" than corporate life. He believed adulthood stemmed from enduring life's minor despairs, not age or trauma, and initially treated Yuji Itadori as a child to preserve his youth. Though trusting Satoru Gojo, Nanami openly stated he did not respect him, citing Gojo's frivolity as incompatible with his own principles. A Grade 1 sorcerer, Nanami's combat strength centered on his innate Ratio Technique. It divided targets into ten parts, creating weak points at the 7:3 ratio for precise strikes. Collapse, an advanced application, destabilized structures like buildings or tunnels, generating debris for large-scale attacks. He also held the record for four consecutive Black Flash strikes, a rare feat amplifying attack power. During self-declared "overtime" (post-6:00 PM), he removed a restriction limiting his cursed energy to 80-90%, wrapping his tie around his hand and fighting with heightened brutality. He demonstrated exceptional durability—surviving Mahito's soul manipulation and Dagon's Domain attacks—and mastered swordsmanship and hand-to-hand combat, effortlessly overpowering foes like Haruta Shigemo. Nanami's relationships were defined by mentorship and mutual influence. Yu Haibara's optimism countered his negativity during their school days; Haibara's death haunted him, cementing his cynical view of sorcery. As Yuji Itadori's mentor, he initially saw him as a liability due to Sukuna but grew to respect his resolve against Mahito. Yuji affectionately called him "Nanamin," and Nanami's final words—"You’ve got it from here"—reflected deep trust. Grade 2 sorcerer Takuma Ino revered him, considering Nanami's endorsement essential for his promotion to Grade 1. In the Shibuya Incident, Nanami fought multiple special-grade curses consecutively. Surviving Dagon's Domain left him severely injured before Jogo's flames critically burned him. While battling transfigured humans, Mahito confronted him. Fatally wounded, Nanami envisioned Haibara, who gestured toward Yuji. Entrusting Yuji with his final words, Nanami perished at Mahito's hands.