Fedya's Goal

We know that our dear Fedya wants to play Wanda from the X-Men and wipe out all the ability users. For that, he needs the book if he doesn't want to go killing one by one. But first, he appears to have other goals, like ending the Port Mafia and the Armed Detective Agency. With the cannibalism arc we thought “oh okay his plan failed” but at the end of the arc you can see that everything was going fine for him, even though he appeared to be surprised at the betrayal of Fitzgerald and Dazai finding out about his location.

To be honest, Fitzgerald's betrayal must have surprised him, as at the beginning of the whole manga story, at the end of chapter 12, we see that Fitzgerald, Agatha Christie and Fedya are together to capture Atsushi as he appears to be the key to the location of the book. With Fitzgerald being defeated, Fyodor was one step closer to having the book for himself.

Now, realize this, Fyodor is constantly allying himself with people who don't share his main goal. Fitzgerald wanted the book to bring his daughter back to life and rebuild his family. Fukuchi used the book page to turn the ADA into criminals but mainly to try to destroy the world's governments and put them all in a great war. We don't know why Agatha wants the book but it probably doesn't align with what Fyodor wants either.

And then, we realized that he only uses these people. Fitzgerald, Agatha, Fukuchi, Kolya, Sigma; they're all just pieces he needs to discard when he's finished using it, so much so that he asked Kolya to die at the end of his participation in the plan & put Hawthorne to kill Sigma. When Fyodor no longer needs the pieces, he kills them.

And Fyodor made it clear in chapter 42 that his first target is the Porto Mafia and then he would focus on the ADA. And it makes sense. We know that, even without any will, both organizations can coexist and even form an alliance if something is too fucked up for just one of them to resolve. But with the ADA focusing totally on the prosecution issue of being criminals AND fighting a god of war AND a vampire pandemic (lol I love to say that) it turns out to be kind of hard for them to help the Port Mafia that's being slaughtered - I believe - by the vampires. Mori even let the Agency solve Fukuchi's case and helped them in the best way because he knows he's in deep shit.

In addition, Fyodor also has documents on ALL mafia abilities users, which include Chuuya and Verlaine who are/were constant targets of Europe.

Fedya's Plan

"Okay, crazy person who won't shut the fuck up, you've already said that Fyodor's goal is not to end the world's government system nor rebuild his dead family, we know he wants to wipe out the ability users and that he has a god complex, so what? Why don't we get rid of Fukuchi yet? Why is he so special?"

Fukuchi has two purposes in this arc:

To destabilize the strong ties of the ADA (ex: Fukuzawa and Ranpo)

To bring prestige to the Order of the Clock Tower

Fyodor knew about the strong connection Fukuchi and Fukuzawa had because Kolya spent those six months in government and obtained this information from Minister Tonan. Other people in the government also seem to know about Fukuzwa's past as one of the swordsmen trained for war.

To summarize: Fukuzawa and Fukuchi know each other as they were trained from a very young age to be government swordsmen. This is explained briefly in the novel about the origins of the Agency and it is easy to connect the dots with the last chapters of the manga where it is briefly shown that Fukuchi and Fukuzawa went their separate ways and bla bla bla.

The Fukuzawa-Ranpo relationship could be destabilized because Ranpo already comes with a heavy weight on his shoulders about being the agency's savior from the cannibalism arc, showing how he doesn't want to accept the DoA case for putting his partners in danger and how he put it all to waste by completely relying on Fukuzawa's judgment of Fukuchi. Also, with Mori's request for someone from the Agency to go to the Mafia and with him saying that "Fukuzawa left him free to choose", the trusting relationship between Fukuzawa and Yosano could also get a bit destabilized.

And, going further with my memory, the Agency's own ties to the Government and the people of Yokohama could be destabilized as they plan to expose Yosano's past with war, Kyoka's crimes, Dazai's past as a Port Mafia executive, and the murders Fukuzawa committed, as well as having been in partnership with the current mob boss at some point in the past.

So ok, Fukuchi's first purpose is to serve as the pivot of the ADA's relationships. But why would he serve as a trophy for Agatha organization?

Come on, how much honor would a person/organization gain if they unmasked the supposed world hero who plans to end the world's government system, in addition to ending a vampire pandemic that is terrorizing the world, IN ADDITION TO acquitting a poor Japanese organization that has been suffering accusations of terrorism even though it's just a victim? The true saviors of the world, enter the Order of the Clock Tower!

As I already said, we know that Fitz, Fedya and Agatha were allies to get the book. With Fitz being sidelined with the defeat of his plan, Fedya and Agatha had probably already established that it would be just the two of them even before Fitz's defeat.

And we also know, with the beginning of vol 14 that Fedya was arrested on purpose, he let himself be taken to Mersault. And Mersault is where? Exactly, in Europe, probably France or England, which are the only ones that matter (lol).

"But why would Agatha accept something like that?" You, person with little logical reasoning and a very bad memory, ask me and I am very happy to answer. Agatha and her organization have suffered a major damage to their reputation as the Queen of Great Britain, who lives under their protection, was one step away from death by murder. And guess who almost murdered this old lady? Exactly, Paul Verlaine who was once one of the biggest terrorists in the world and now lives under the control of the Port Mafia. Obviously is not a big reason, but if someone offered you a plan that would grant you the honor of being the savior of the world, destroy the guy, and his organization, that irreversibly destroyed your reputation years ago and still get one step closer of getting a book that alters reality, what the hell do you say? No, thank you?

Summary (because I think I said nothing to nothing)

"Why has Fukuchi won every fight so far?" So that the real guy to defeat him is Agatha and she would win the prestige of having unmasked the war hero and saved the world.

"So Fyodor's plan is?" Let Agatha strike terror while he waits for the right moment to fuck her up, like he did to Fitzgerald.

"Why did Fyodor's face appear in the last chapter?" That was probably a ploy to show that Fedya is behind the Bandana and Eye Patch murders but he didn't actually kill them.

"Can a ability have such a range to hit people on an airplane?" Yes, but not Fyodor's. Remember Ayatsuji from the novel Gaiden? So that guy's ability comes down to finding the culprit in a murder case and that culprit will die from an accident, like a prophecy, and that skill can affect anyone anywhere in the world.

"So it was Ayatsuji?" Obviously not, but if there is an ability that affects ANYWHERE IN THE WORLD it is possible that one of the most powerful organizations in history - Agatha's one - also has someone with a similar ability.