Clair Aoki is a fair-skinned young woman with long light brown hair, brown eyes, and distinctive facial freckles. Her physical figure is notably more pronounced than her older sister Elena's. Elena murdered their parents, disguising the deaths as a gas leak, an act causing Clair severe psychological trauma. This trauma triggered Clair's initial suicide attempt, interrupted by Shuichi Kagaya. She subsequently lived alone in a small efficiency apartment. Later revelations confirmed Clair and Elena are paternal half-sisters due to their father's affair with Clair's mother, complicating their dynamic. Clair's motivations center on uncovering the truth behind Elena's monstrous transformation and avenging her parents. Initially presenting a manipulative, tomboyish, and emotionally detached personality, Clair viewed Shuichi primarily as a tool. She displayed abusive tendencies towards him, masking a ruthless willingness to kill without hesitation or remorse beneath a perverse cheerfulness, unsettling Shuichi. Pragmatic about survival, she blackmailed Shuichi upon discovering his monstrous transformation ability. She frequently entered his hollow canine-like form, often minimally clothed or in lingerie, to control his movements in combat, demonstrating a disregard for conventional boundaries. Despite physical weakness, her strategic mind and use of Shuichi's abilities made her an effective combatant. Over time, her relationship with Shuichi evolved from mutual distrust into a profound emotional bond. She developed genuine care, vowing to kill herself if he died first to remain together eternally, signaling emerging romantic feelings. This shift coincided with increasing possessiveness and jealousy towards other women interacting with Shuichi. Clair's journey reflects a gradual, fractured emotional reconnection, though her capacity for violence persisted. Clair possessed no innate supernatural abilities initially, relying solely on tactical intellect and Shuichi's monstrous form for combat effectiveness. Inside his hollow body, she gained enhanced physical capabilities—superhuman strength, speed, and reflexes—while controlling his movements. Her instant mastery of this symbiosis contrasted with others' struggles. Later, using an alien coin, Clair acquired superhuman reflexes and the ability to slow her time perception, enabling lethal precision in combat. A significant development was Clair and Shuichi achieving complete fusion into a single entity wielding a katana, requiring extreme emotional synchronization triggered by near-death experiences or profound resolve. This fused form exhibited vastly amplified power, capable of defeating regenerating opponents like Kaito. Clair's progression from vulnerability to formidable fighter underscores her central role confronting threats tied to the alien coins and Elena. Her relationship with Shuichi forms her core development. Starting as antagonistic collaborators bound by necessity, their dynamic shifted through shared trauma and battles. Shuichi's inherent kindness and vulnerability gradually penetrated Clair's emotional barriers, fostering mutual dependence. Her possessiveness manifested as fierce protectiveness against threats from Elena or other women like Chihiro Yoshioka. Clair's interactions with Elena are defined by betrayal and lethal intent, underscored by Elena's twisted protective love. Clair’s discovery of their biological connection through their father’s infidelity layered this conflict without diminishing her drive for retribution. Other characters, like Nana Mifune, intersected peripherally. The alien coin quest and encounters with other "Collectors" catalyzed Clair’s strategic decisions and moral compromises, including later conscience-weighing acts of mass murder for survival.