Ace

A (pronounced "Ace") (エース,) was one of the Port Mafia's Executives.

Appearance
A is a young man with short, light straight hair, but bangs parting in the middle of his face. Part of his hair covers his right eye.

As most of the mafia, he dresses formally.

Personality
Though he is an Executive, he has no loyalty towards the Port Mafia and even tried to recruit Fyodor in his attempt to rebel against the mafia. He is shown to be a very cocky person.

Despite his arrogance, A is intelligent and observant. He notices the inconsistencies of his base since Fyodor's arrival, from the door lock to the frozen clock. Having his intelligence underestimated greatly insults A, and he is prone to violence as a result.

Ability
A's ability, The Madness of the Jewel King (宝石王の乱心,), is an ability that turns his subordinates' life (those who equip the collar he gave) into jewels which worth according to the target's lifespan.

Background
A started as an astute, clever gambler that dominated one of the Port Mafia's casinos. He bribed authorities a great deal of money, quickly rising to the rank of Executive within the mafia. However, he is internally recognised by the mafia as nothing more than a bodyguard rank.

Plot
A appears reporting the capture of the Fall of Moby Dick's mastermind, Fyodor Dostoyevsky, to Ōgai Mori and Kōyō Ozaki. He describes the man as a "soulless, vampire-like man", but keeps his thoughts to himself rather than further elaborate to Mori.

Mori suggests leaving Dostoyevsky to Kōyō and her torture squad, but A insists to take care of him himself. This surprises Kōyō, who points out majority of the Executives stayed out of the war against The Guild. A retorts by suggesting it would have only been right if Executives were the ones captured instead, greatly antagonising Kōyō. Before their debate goes any further, Mori abides, leaving Dostoyevsky in A's hands, much to A's pleasure.

Kōyō questions Mori's decision, given A's disloyalty and deceptions against the Port Mafia for his own financial gain. Mori, however, counters that financial gain is A's strong suit, so they should wait and see what A has up his sleeve.

In the depths of the mafia's HQ, A greets Dostoyevsky and introduces himself as A. Taking a knife, he cuts off the restraints, ridiculing his subordinates for treating a "guest" in such a way, ordering drinks and clothing for Dostoyevsky.

After Dostoevsk is dressed, A claims to be a lonely man. The mafia distrusts him, and he distrusts the mafia. The only thing he trusts are his games of chance, the jewels in his vault, and his private force fifty men. He refers to the man as the "51st" person he can trust, and invites Dostoyevsky to join forces with him in killing Mori.

Dostoyevsky does not agree, instead threatening to kill A. A snaps, breaking a bottle on Dostoyevsky's head. Clenching his fist, A demonstrates his ability. One of his subordinates suddenly falls to his knees in pain, and A's turns him into an array of jewels. He claims it's an ability overflowing with benevolence. The collars his subordinates wear, A explains, are put on of the subordinate's own agreement, but cannot be taken off. He orders his remaining subordinates to clean Dostoyevsky up, and claims that if he agrees to put a collar on, A won't kill him. He then leaves the room for some time.

When A returns, Dostoyevsky suggests they play a game. Dostoyevsky is confident A cannot kill him because A wants information on his group's next move and finances, logic A understands.

A decides the games of the rules: Dostoyevsky draws first, guessing the card to be low correctly, and the card after that as well. Both times A counts only as luck. However Dostoyevsky continously guesses correctly, and ends up with all the cards, A never having a turn whatsoever. Throwing a fit, A orders for Dostoyevsky to have his "swindler limbs" cut off.
 * 1) Take one playing card at a time from the same deck.
 * 2) Guess if the card will be lower or higher than the previous card.
 * 3) If the guess is correct, the guesser goes again.  If incorrect, the other player draws.
 * 4) When all cards are drawn, the player with the most cards wins.
 * 5) If A wins, Dostoyevsky leaks information.  If Dostoyevsky wins, A grants him his freedom.

This proves impossible. Dostoyevsky initiated the game, antagonising A the whole way, to stall for time, and now the Rats in the House of the Dead run the underground base. Dostoyevsky bargains that if A hands over the jewel vault's key, he will survive. A, undeterred, reveals that his base isn't on mafia territory, nor is it truly underground. In fact, he claims it to be on a ship at sea. Apparently, its equipment was used to during an an ability users' war, presumably the one eleven years ago. Thus, suppression of its current group would be impossible without an uproar.

A reveals he wiretapped Dostoyevsky's conversation with the boy, and knows Dostoyevsky can lock his enemy's consciousness inside his own head, hence why he was so lucky in the card game. His proof being the lack of uproar on the ship that he should have heard, the door not opening whatsoever, and the clock, which hasn't worked since A returned.

A brags about overcoming Dostoyevsky's ability, calling himself a "king by birth" thanks to knowing all there is to know about Dostoyevsky. With great pride, he reveals he knows how to free himself of Dostoyevsky's ability: 'killing' himself in the man's mind, and waking up alive in the real world to kill Dostoyevsky. He takes the wire off a lamp and hangs himself with it.

Instead, Dostoyevsky leaves the room of his own volition, revealing to the shocked boy he tampered with the room all along, and that his ability is not locking a person's consciousness in his own. Ultimately, this means A hung himself and died.

Trivia

 * The Madness of the Jewel King refers to A himself, however it is likely the title comes from the play The Madness of King George III, a play by Alan Bennett. Likely to avoid copyright complications, A's ambiguous name and ability name focus strongly on the character, rather than the author.