Noi operates as an elite magic user and professional cleaner for her older cousin En, working primarily in the Hole alongside her long-time partner Shin. She sports silver-white hair, red eyes, and an exceptionally tall, muscular physique that often causes initial gender confusion until she speaks or removes her mask. Her signature attire includes a blue zip-up tracksuit marked with her name, gloves, sneakers, and a form-fitting blue gimp mask resembling an exposed skeletal mouth, frequently patched with duct tape; she also wears duct tape around her forearms and calves and has multiple ear piercings. For formal occasions, she switches to leather or form-fitting outfits but struggles with high heels. Confident, fearless, and carefree in combat, Noi frequently disregards defensive tactics due to her regenerative powers, actively enjoying physical confrontations. She often engages Shin in friendly kill-count competitions during missions. Despite her bold nature, she holds deep respect and unwavering loyalty toward Shin. She expresses interest in befriending formidable individuals she encounters, even designated targets, though mission constraints usually prevent it. Her large appetite and preference for fair fights are consistent traits. Her rare healing magic grants near-instantaneous regeneration from severe injuries like limb loss, functioning without conscious activation of her magic smoke and rendering her nearly invulnerable to physical harm. This ability extends to others: she repairs Ebisu's frequent injuries and revives decayed corpses for identification, though she cannot restore life. She also demonstrates object restoration, such as fixing Shin’s melted hammer. Complementing her magic is immense physical strength, enabling her to smash through solid walls, bisect opponents bare-handed, and lift 400-pound objects single-handedly. Identified as En’s younger cousin and only known relative, En exploited her healing talents for his enterprises from a young age, fostering resentment in Noi despite his occasional care. Recruited by the Devil Duston for devilhood training in her youth, she wore cumbersome armor that warped her personality toward violence. Nearing the final exam stage—requiring a year without magic—she broke the rules to heal Shin after catching him stealing food, forfeiting her chance at becoming a Devil. Shin later joined En’s organization as her partner, solidifying their bond through shared missions and mutual disdain for En’s methods. In her present role, Noi undertakes assignments ranging from assassinations to intelligence retrieval for En. Key missions include confronting the magic-immune Kaiman and his partner Nikaido after their attacks on En’s subordinates; during these encounters, she overpowered Nikaido but voiced admiration for her skills. She also participated in locating Kaiman’s severed head, healing it to expose the identity of "the man inside the lizard’s mouth." Her activities often involve navigating interpersonal dynamics, such as renewing contracts with Shin after escaping kidnappers during the Blue Night festival.