Ace, alternately known as A, held the position of financial executive within the Port Mafia, overseeing the syndicate’s fiscal operations. His rise stemmed from a history as a shrewd gambler who controlled one of the Mafia’s casinos, exploiting bribes to authorities to secure his swift promotion. Though occupying a high-ranking role, he secretly orchestrated a coup against leader Ōgai Mori, compiling a dossier of members’ abilities—including Mori’s—to fuel his insurrection. Physically, Ace appeared youthful, with ash-blonde hair styled to obscure his right eye and piercing purple eyes. His formal Mafia attire featured a gray vest, purple tailcoat, and black necktie adorned with a ruby clasp, complemented by white gloves and gold vertical earrings. Arrogant and calculating, he treated subordinates as disposable resources, perceiving their lives as transactional commodities via his ability. This mindset bred mutual animosity with peers such as Kōyō Ozaki, who condemned his absence from frontline operations during the Guild conflict and questioned his leadership legitimacy. Ace’s ability, *The Madness of the Jewel King*, converted the lifespans of collared subordinates into gemstones of differing worth. The specialized collars, irreversible once attached, enslaved wearers to his command until their demise. The ability’s title loosely alludes to *The Madness of George III*, though this link remains intentionally ambiguous. His narrative climaxed during the post-Guild arc, when he volunteered to interrogate captive Fyodor Dostoevsky. Attempting to enlist Fyodor for his rebellion, Ace divulged his distrust in the Mafia, reliance on mercenaries, and dependence on his jewel stockpile. After Fyodor rejected his offer, Ace transmuted a subordinate into jewels, then challenged him to a card game. Fyodor manipulated Ace into believing they were trapped in a mental illusion, persuading him suicide would shatter the delusion. Ace fatally hanged himself with a lamp cord, unaware of Fyodor’s ruse. Nicknamed for his gambling expertise, Ace’s unconfirmed true name mirrored his delusional self-image as a natural-born “king.” His hubristic conviction in inherent superiority blinded him to Fyodor’s cunning, culminating in his demise—a testament to the peril of overconfidence within the Port Mafia’s volatile hierarchy.