Fyodor Dostoevsky/Synopsis

History
In the past, Fyodor was mentioned to have been met Osamu Dazai at an unknown point in time. Three years prior the main timeline, Fyodor first met Sigma, who had been born by power of the Book. The Russian asked him if he wished for a home, an offer that Sigma accepted.

Later, Fyodor apparently allied himself with the Guild in an attempt to acquire the Book, presumably together with the Order of the Clock Tower.

The Guild Arc
Fyodor is first seen when discussing the operation with Francis Scott Key Fitzgerald and Dame Agatha Christie, mentioning that he has foreseen the events that took place earlier.

It is unknown what he was doing during the war. Nevertheless, when Atsushi Nakajima and Ryunosuke Akutagawa battled against Fitzgerald, Fyodor accesses Moby Dick's controls and forces the warship into a free-fall after the latter's defeat. Sometime later, after taking a quarter of the Guild's funds, he encounters Nathaniel Hawthorne and together they make a deal to help each other as long as Margaret Mitchell gets proper treatment. Agreeing to his condition, Fyodor states that his next step is to cleanse Yokohama of the sinners.

The Guild Aftermath Arc
Spreading disinformation about the leftover Guild's fortune, his plan is set in motion in order to lure criminal organizations and bring a wave of crime. Dazai states this truth, while a focused Fyodor is somewhere at the bay staring at the sea. Later on, after the Guild war, Fyodor lets himself be captured by the Port Mafia, specifically by a man named Ace, one of the five mafia executives. While the executives and the leader discuss his fate, he is detained in an underground prison.

Ace shows himself to him, stating his name. Fyodor then is set free and brought to talk to the man about joining forces together to destroy the mafia. Nevertheless, he promptly denies and then threatens the executive to kill him, which angers the executive and is then hit by a bottle of wine. The man leaves, leaving only Fyodor together with a young boy named Karma, who dries him up and converses with him.

After Ace returns, he is surprised to see the Fyodor eager to play a game of High or Low, which he wins flawlessly. Angered by this, Ace orders his subordinates to come, but then is taken aback by the fact that nothing appears to be working. He is then deluded by Fyodor into thinking that it is the work of his ability.

Ace is tricked into committing suicide after coming to the conclusion that it is the only way to escape Fyodor's supposed ability (the ability to lock others in your consciousness), where in actual fact, Fyodor had set up the room around them in order for it to seem like a false reality. He leaves Ace's body and escapes the room where he encounters Karma, who is shocked by the fact that Fyodor has beaten Ace. It is revealed that Fyodor purposefully leaked information of his false ability and a way to escape the false ability to the kidnapper in order to trick Ace.

He proceeds to reveal his true motive, gaining a list of the Port Mafia members and their abilities, which Ace compiled as a part of his plot to take over the mafia. Stating that the list's value will be halved if the mafia were to know that he owned it, Fyodor states that he must not leave any witnesses. He uses his ability to instantaneously kill the young boy and calls himself as a God while leaving the burning cruiser and stating his next objectives: the annihilation of the Port Mafia and then, the Armed Detective Agency.

Two months before the operation that would be known as the Cannibalism strategy, Fyodor heads to the Seventh Agency and breaks out Mushitaro Oguri, a gifted captive with the ability to erase evidence in crime scenes. Mushitaro agrees to partake in the operation upon several personal conditions, all of which Fyodor agrees to.

Cannibalism Arc
Following the attack of Fukuzawa by a masked assassin, Fyodor disguises himself as a policeman. After the car that Mori and Elise plan to drive off in explodes, policeman Fyodor comes to "investigate". He asks an unsuspecting Mori about the cause of the explosion and when answered, asks Mori if he is okay. Fyodor then proceeds to stab Mori. While Mori is falling, he knocks off Fyodor's police hat to reveal his true identity. Fyodor runs away and Elise loses sight of him because of the large crowd of bystanders.

Fyodor runs into an alley and sheds his police disguise, changing into his usual clothing. He searches a compartment in the alley where he placed his Ushanka-hat only to find that it isn't there. Dazai appears and Fyodor instantly recognizes him. Dazai, having figured out his plan, states that it is just like Fyodor to tamper with the mind of Hawthorne and turn him into an assassin. Dazai reveals that Fyodor's aim is to obtain the mysterious Book, but first, he has to exterminate Yokohama's ability users. Since the 'Rats' don't have the firepower to burn down the town like the Guild, Fyodor took out the heads of the Agency and Mafia through assassination. Fyodor asks Dazai how he came to such a conclusion and Dazai says that it's 'because it's what I'd do'. Fyodor smiles and asks Dazai if he's suggesting that they're alike.

Fyodor tells Dazai that the poison given to Fukuzawa and Mori 'assures mutual destruction'. He says that he won't destroy the two organizations- they'll do it themselves. He explains that the poison is from a virus-type ability held by a certain criminal friend of his. Over 48 hours, their bodies' microfauna grows and eats away at the internal organs of both hosts. However, if either host dies before the 48 hours ends, the ability will stop.

Fyodor states that people are 'sinfully stupid' and despite knowing they're being manipulated, they will continue to kill each other, nevertheless. He says that someone must rid them of their sins. Suddenly, a sniper shoots Dazai and he realizes that Fyodor predicted his actions. Fyodor tells Dazai that his vitals weren't hit because he still has a part to play in his plan. Then, Fyodor realizes Dazai knew the sniper was there. Dazai says that the Book is a single book of blank pages where anything written in it becomes the truth. Fyodor says that he will use the book to rid the world of the sin of ability users. Dazai challenges Fyodor to make that happen. When they hear Doppo Kunikida and Atsushi searching in the alleyway for Dazai, Fyodor leaves the scene.

Fyodor appears where he is seen playing the cello to Shōsaku Katsura. It is revealed that he gave a bunch of weapons to a man called Alexander Pushkin and his young allies. Pushkin, who turns out to be a fake one, then passes Fyodor's message to the Agency that the rules cannot be changed.

Having been revealed that he is not present in their hideout ever since the beginning, Fyodor leaves a café when he unexpectedly encounters Dazai and Fitzgerald. It then dawns on Fyodor that they used the Eyes of God to track down his location. Fitzgerald reveals that he couldn't stand Fyodor keeping the money he stole from him that he decided to aid the Armed Detective Agency in his capture. Ango Sakaguchi then arrives with some armed men to take Fyodor in custody. As an operative is about to shackle him, the man instantly dies after touching him. Nevertheless, Fyodor decides not to further put up a fight and goes willingly with Ango.

Decay of Angels Arc
Upon his arrest, Fyodor is brought to and detained in the European facility Meursault, where he enacts his plans in the wake of the terrorism plot pinned on the Armed Detective Agency. Utilizing a brainwashed Hawthorne, he attempts to assassinate Fitzgerald to render Eyes of God useless, but he discovers that it has been prevented when Dazai greets him across his cell, ready to engage him directly.

Initially playing around with each other through their coded language, they soon simultaneously ask each other how they are contacting their allies outside, both of which refuse to divulge yet threaten to eventually figure out themselves. Later, Fyodor suddenly asks what Dazai knows of the fifth Hunting Dog, but he notes that he does not know much about him, except that he can manipulate metal. Fyodor is curious how the Agency can fare against such adversary.

During the hunt for the Agency at the Sky Casino, Fyodor and Dazai "play" chess in prison, upon which Dazai remarks on the audacity of Fyodor's move. Meanwhile, Dazai summons his queen piece to the battlefield. Fyodor claims his queen piece to be Lucy Maud Montgomery in the Agency's operation, which Dazai verifies.

Dazai asks why he chose Sigma as his rook, so Fyodor reveals that Sigma has no history; the only known thing about him is his ability. Dazai then conjectures that the page gave birth to the Sky Casino only eight days ago along with its 13-year history. Fyodor quips that the strongest in their game and the scariest thing in the world are those who have nothing else, such as Sigma, an ordinary person filled with desperation. Dazai is unconvinced, so he urges Fyodor to reveal his true aim. Fyodor then tells him that Sigma is born from the Book out of nothing.

With Sigma's fall and the Agency's apparent defeat, Dazai is unsettled with Fyodor, though the latter claims that he merely prayed to God who in turn listened to him. After all, Fyodor asserts that God prefers perfection and harmony, hinting that they placed a line in the Book that all police forces are to disregard any evidence proving the Agency's innocence. Dazai laughs at his comment, retorting that God's gimmicks are accidental and illogical rather than perfect and that those who truly make the world go round are those who persist and fight amidst constant change. He adds that humans may be sinful and foolish but far from boring.