Originally notorious as "Carnage Middle's Murder Weapon" and "Kuboyasu the Demon Killer," Aren Kuboyasu was a fearsome delinquent at his former school. His signature mullet hairstyle and modified uniform, featuring pants resembling an oversized skirt, marked his appearance. His reputation arose from exceptional combat prowess, having defeated every boy in his third-grade class to become their leader, a history that left him with numerous scars later concealed under long sleeves in casual wear. Transferring to PK Academy prompted a deliberate effort to appear normal. He cut his hair short, abandoning the mullet for dark violet, and adopted non-prescription glasses. He maintained a muscular physique at 173 cm (5'8") and 65 kg (143 lbs), wearing a tidier version of the standard male uniform. Kuboyasu possessed a short temper, especially towards rudeness, initially struggling to control his anger; minor incidents could provoke him to throw nearby objects, nearly causing serious harm. His intense fury manifested in a terrifying "devilish face." Contrasting this aggression, he displayed childlike enthusiasm and naivety about motorcycles, willingly helped friends with driving tests, and revealed unexpected domestic skills in cooking and drawing. Interactions with classmates gradually fostered greater calmness and social integration. His delinquent background granted significant abilities: enhanced physical strength and finely honed brawling intuition allowing effortless defeat of multiple opponents. His combat instincts provided heightened situational awareness, enabling him to detect hidden observers—an ability that surprised the series' psychic protagonist. This sensory acuity aligns thematically with his name, an anagram of the Japanese word for "clairvoyance" (kureaboyansu). His family history shaped his character; both parents were former motorcycle gang leaders—his father leading a male gang, his mother a ladies' gang. This environment likely contributed to his mechanical knowledge and early delinquency. He resided in his father's distinctive childhood home. His development showed gradual socialization despite lingering pridefulness, particularly in rivalries with wealthy peers. Initially uncomfortable in social settings, exhibiting reluctance to sit in others' homes, he formed close bonds, notably with Shun Kaidou, who uniquely used his first name. His journey reflected a sustained effort to leave delinquency behind, navigating occasional relapses into aggression. He created baby names ("Akua" and "Marin") derived from aquamarine gems after receiving a love letter. During his reform phase, he worked part-time jobs as a waiter and cashier.