Shusei Kagari was designated a latent criminal at age five during a mandatory Ministry of Welfare medical examination. This judgment led to his immediate confinement at the Hachiouji Rehabilitation Center, a sacrifice for societal stability under the Sibyl System despite his lack of criminal inclinations. He remained isolated for 14 years. A significant memory from this time involved an unnamed friend in a neighboring cell; they communicated through lip-reading games until the friend was killed during an escape attempt. Facing perpetual isolation in 2110, Kagari chose to become an Enforcer with Division 01 of the Public Safety Bureau's Criminal Investigation Department, accepting the role of a "hunting dog" for high-risk operations over continued incarceration. Physically, Kagari stood 165 cm tall and weighed 53 kg. He had spiky orange hair often secured by teal barrettes arranged as Roman numerals for 12. His standard attire included a black jacket, red tie, and CID windbreaker during field operations. He possessed above-average physical capabilities, including 2.0 eyesight and a 50-meter sprint time of 6.3 seconds, excelling in soccer. Kagari displayed a carefree, jocular demeanor, serving as Division 01's primary lighthearted figure. He frequently teased colleagues like Inspector Akane Tsunemori, whom he addressed by her first name. His leisure time involved playing portable video games resembling a PlayStation Portable; he favored first-person shooters, fantasy RPGs, and secret adult-rated games. His hobbies included cooking and analog games maintenance, with taco rice topped with fried eggs cited as his specialty dish. He enjoyed sweets but strongly disliked spicy foods and kiwifruit, even fainting from overly spicy curry. He adhered to mottos like "Whatever you do, you have to enjoy the process" and "Life is just killing time until our death," reflecting his resigned outlook. Beneath his cheerful facade, Kagari harbored deep resentment toward the Sibyl System and the society that condemned him. He openly expressed apathy about societal safety and welcomed Sibyl's destruction, yet despised heinous criminals like Shogo Makishima, particularly after the murder of fellow Enforcer Mitsuru Sasayama. His bitterness extended to those taking freedom for granted, stemming from his lifelong exclusion. Despite this, he demonstrated loyalty to Division 01, risking his life for colleagues and later acknowledging it as his place of belonging. His combat skills emphasized raw strength over technique, as observed by Shinya Kogami. Their initial confrontation ended with Kagari's broken arm and Kogami's broken ribs, but they developed mutual respect and friendship afterward. Kagari also shared a sibling-like bond with Enforcer Yayoi Kunizuka. During an investigation into NONA Tower, Kagari discovered the Sibyl System's true nature as a collective of disembodied human brains. To preserve this secret, Chief Joshu Kasei deliberately overrode her Dominator's standard paralyzer setting, deploying Destroy Decomposer mode to eliminate him. His official status was listed as "missing" during the riot investigation, though his remains were disintegrated. Only Akane Tsunemori learned the truth of his death, concealed by the Sibyl System from Division 01. In *Sinners of the System*, Kagari is listed among the characters but receives no substantive development or backstory expansion beyond his established arc in the primary series.