The room had gone quiet, and the atmosphere was heavy as the ceremony unfolded. The time had come to pay tribute to the nine soldiers who had survived the battle of Shiganshina, and the countless others who had not.
As Historia began to pass out the medals one by one, Eren found his mind wandering.
What are we supposed to do now? We had to sacrifice so much to learn the truth about this world, and the truth is terrifying. Having human enemies out there wouldn't necessarily be so bad, but knowing it's the entire world against us…
He looked up as Historia stepped in front of him. She leaned forward and gently placed the medal around his neck.
The odds were never in our favor, but things have only become more bleak. If only...if only we lived in a world that didn't hate us.
Eren lightly kisses Historia's hand.
In the Paths realm, Ymir let out a mischievous grin.
The second his lips made contact with her skin, a bolt of electricity shot through Eren, and he immediately collapsed at Historia's feet, his consciousness leaving him.
Historia's eyes widened in shock. "What?"
"Eren!" Mikasa cried.
The next second, Armin also fell to the floor, his body going limp.
"Armin?" Sasha asked uncertainly.
But before the others could react, the ground began to violently shake, throwing people off balance. Many were able to stay standing with difficulty, while others were unable to and fell.
The shaking grew more and more violent, and for a moment it seemed like the foundations of the building would surely collapse from the extreme vibrations. But then, just as suddenly as it had begun, the shaking stopped.
Everyone was silent for a few seconds, as if afraid speaking would cause the shaking to resume. When it didn't, uneasy murmuring swept through the crowd of military personnel.
"W-what was that?!" Connie whispered.
Hange shook her head, unsure of how to answer.
Numerous members of the Garrison dispersed to check the structural integrity of the building, to calm any panicked civilians, and to try to find out what had caused the shaking. Meanwhile, Mikasa picked up Eren, while Levi picked up Armin, and they carried them over to the medical wing of the building.
As everyone left the room, they were all left with one question.
What was going on?
Boris looked around wildly. "What was that shaking?"
Hitch's eyes widened. "Maybe Annie escaped!"
Boris glanced at her skeptically. "That felt too big to be just a 15 meter Titan. Besides, the building seems undamaged."
Hitch began to jog down the hall toward the basement. "Well, let's check just to be safe."
"Alright, alright."
They quickly descended the stairs, passed by the two guards without a word, and went straight for the door leading to the chamber containing Annie's crystal.
After hastily cycling through the keys, Hitch slammed it into the lock and pushed the door open.
As soon as the door swung open they were stunned by what they could see, or rather by what they couldn't see.
Annie's crystal was gone.
Boris swore. "Shit, looks like you were right. I'll spread the alarm."
Boris dashed back up the stairs to alert the rest of the MP and Garrison soldiers of Stohess about Annie's escape.
But as Hitch looked around, she realized that something wasn't right. The door to the chamber had still been locked, and appeared to be completely undamaged.
And as she walked down into the chamber and examined the walls, she noticed that not only was there no sign of the crystal, but there was no indication of any sort of tunnel or hole or anything. The walls looked the same as they always had.
It was almost as if Annie had just vanished into thin air. But that wasn't possible.
Was it?
As Hitch stepped near the exact spot where Annie's crystal had been, and was looking at the wooden stakes and chains that had kept it in place, she noticed something strange right in the middle.
It was a fruit.
Curious, she bent down and picked it up. As she examined it more closely, she could see that it looked like a peach, except that it was a reddish pink color, and had strange swirls covering its surface.
The fruit seemed pleasant, enticing, and on a whim Hitch took a bite out of it.
She instantly regretted her choice.
"Bleh! Gross!"
The fruit tasted incredibly sour, and while she had been unable to stop herself from swallowing the first bite, she quickly dropped the rest of the fruit to the floor.
Hitch made a face. "What the hell was I thinking, eating some strange fruit off the ground."
She turned around, her mind turning back to Annie, and the conundrum of how the Female Titan shifter could have escaped.
She let out a long sigh.
What is going on?
In Trost, the residents not only noticed the violent shaking, but also something even more unusual.
After the shaking subsided, the boulder sealing the outer gate was gone, and the gate looked brand new, as if it had never been destroyed by the Colossal Titan.
One of the Garrison soldiers looked at the gate in astonishment. "What the hell is this? There was that strange quake, and now the gate has magically repaired itself? What's happening?"
Rico shook her head. "I don't know."
Ignoring her comrades, Rico used her gear to descend down to the base of the wall in order to get a closer look at the gate.
As she got near, she was amazed at how good it looked.
She frowned. "But what could have caused it to reappear like this? Even the Titan powers can't truly make something come from nothing, there's always a source for everything."
She stopped near the edge of the gate, and as she looked at it more closely she spotted a fruit on the ground just in front of the gate.
"Hmm? What's this?"
She bent down to pick it up. It appeared to be a golden apple, but the coloration seemed slightly off, and there were strange swirls covering the skin.
On a whim, she took a bite.
Her face scrunched up, and she held the fruit at arm's length.
"Ugh. Whatever this is, it's not fresh. I guess eating a random fruit on the ground was pretty stupid."
She paused, and looked at it more carefully. "Although...is it just a fruit?"
As she examined it, she realized that something about the color was bothering her. She'd seen the color once before, in some of the drawings she'd seen of the Armored Titan that had been based on eyewitness testimony.
Of course, it's not like there was any connection between the Armored Titan and this fruit.
Was there?
She looked at the fruit, then back at the newly repaired gate, a thoughtful frown on her face.
"Something strange is going on."
Eren let out a low groan, and slowly opened his eyes. As he looked around the room, he could see that he and Armin had been placed on adjacent beds in the medical wing, with the other survivors anxiously watching them.
Armin slowly sat up, having regained consciousness at around the same time that he had.
Sasha smiled at them in relief. "They're awake!"
Jean shook his head. "Don't scare us like that."
Mikasa stepped forward, and looked back and forth between the two boys frantically.
"Are you okay?"
Armin slowly nodded. "I think so."
Eren rubbed the back of his neck. His body felt strange, different somehow, but he wasn't sure how to put it into words, and overall he felt fine, so decided not to worry them.
He cleared his throat. "What happened?"
Hange grimaced. "You both collapsed in the middle of the ceremony, and right afterwards there was a massive earthquake."
"What?!" Armin exclaimed. "Is everyone okay?"
Hange raised her hands reassuringly. "Yes, everyone's fine, the earthquake didn't appear to do any damage, apart from scaring the hell out of us. But some odd things have occurred."
Eren frowned. "Like what?"
A troubled expression came onto Hange's face. "For one, Annie's gone. But it's strange. The door to her cell was still locked and undamaged, and there were no signs of a tunnel or any other way out of there. It's as if she vanished into thin air."
"Also, the gate at Trost appears to have magically repaired itself." Jean added.
Armin looked utterly baffled. "Huh? How is that even possible?"
Hange shook her head. "I don't know. My only guess is that it has something to do with the power of the Titans, but even so, there was nothing in Grisha's notes that indicated this sort of thing is possible."
She turned toward Eren. "Unless...Eren, is it possible that you somehow unlocked the Founding Titan's power?"
Eren looked down at his hands. While it was true that he'd felt a strange bolt of electricity right before the earthquake had occurred, it had been completely different from the feeling he'd had when he'd inadvertently awakened the Founding Titan's power from touching Dina's Titan.
He also wasn't entirely sure if that was indeed the reason he'd been able to use the Founding Titan's power, and until he was sure, he would continue to keep it to himself, as he didn't want to put Historia in danger for no reason.
Eren shook his head. "No, I don't think so."
"Hmm." Hange murmured.
About a week later Connie and Sasha journeyed on horseback to what was left of Ragako in order to check on his mother. Given all the strange things that had occurred in the wake of the earthquake he wanted to make sure she was okay.
Or at least, as okay as she could be as an abnormal Titan.
While the strangest things had happened on the day of the earthquake, there had been some other odd changes that they'd noted.
In particular after Hange started doing further experiments with Eren and Armin's Titans, they'd noticed some things that had changed about their powers. For one, an injury was no longer necessary to transform. For as long as they had known about the Titan powers, drawing blood had always been a requirement to transform, with a goal or objective being the secondary requirement. Yet now, only having the goal or objective was necessary for them to transform, with the injury becoming entirely optional.
Another noticeable change was that their stamina seemed significantly higher than before. In Eren's case he could now transform four times in a row instead of three, and even after four transformations he didn't seem anywhere near as exhausted as he had during their earlier experiments.
As for Armin, they didn't have as much data to go on. But from what little they knew about the Colossal Titan from Bertolt and Grisha's journals, the Colossal Titan only had the strength to transform about once a day, with maybe a partial transformation being possible if given several hours to rest. However, Armin was able to do a full transformation twice in a row, and even managed a partial transformation shortly afterwards.
All of it pointed to one conclusion: whatever had happened on the day of the earthquake, it had drastically affected many things, including the power of the Titans.
Which made Connie all the more anxious about his mother. It was true that the normal Titans wandering outside of Wall Rose appeared to be behaving the same as always, but he couldn't shake the feeling that something had happened in Ragako.
As Connie and Sasha rode into the abandoned village, Connie felt his stomach drop as he took in the sight of his empty house.
"What? Where is she?"
He leaped off of his horse and ran around the perimeter of his house, looking around frantically.
But there was no mistaking it. His mother was gone.
"No…" He whispered. "Did someone kill her? Damn it...I suppose...but…"
He shook his head hopelessly.
Sasha walked over to him, her eyes sad.
"Connie…"
Connie wandered into his ruined house dismally, his mind involuntarily bringing back memories of a happier time, when the house was still intact, and his parents and siblings were alive and well.
Now all of that was gone, and he was the only one left. And it was all because of that fucking monkey.
He glanced at a nearby small cabinet that was somehow still standing, and he froze when he noticed something sitting on top of it.
Lying on the wooden surface was a fruit. It looked a bit like a pomegranate, but it was a dark brown, and it had strange swirls all over it.
As he looked at it, Connie found the coloration of the fruit reminding him of the color of the Beast Titan's fur.
Gritting his teeth in anger, Connie stomped over to the cabinet and picked up the fruit to hurl it at the wall in an effort to vent some of his feelings.
But as he picked it up, he immediately noticed that it was heavier than he was expecting, and there was an unusual, almost unearthly quality about it.
Sasha stepped into the house, and eyed the fruit warily.
"What is that?"
"Dunno." Connie murmured.
His curiosity getting the better of him, he took a bite.
He flinched as the bitter taste burned his throat. "Shit, this tastes nasty!"
Sasha let out a small smile. "Heh, and I'm usually the one who can't resist food."
Giving into his earlier impulse, Connie hurled the fruit at the wall as hard as he could, where it splattered against the weathered wood, leaving an unpleasant looking stain that slowly slid down onto the floor.
Connie felt involuntary tears sliding down his face, and he shut his eyes, unable to look at his ruined home any longer.
Sasha gently placed her hand on his shoulder, trying to give him what comfort she could.
Several more weeks passed, and for a while Hange felt that while they still didn't entirely know what was going on, no more new strange developments would occur.
Then one morning, a new strange development occurred.
Hange looked up to see Levi striding into her office, and at once felt her back stiffen. Levi's face was not irritated or indifferent, as was typical for him, but instead slightly bewildered.
Levi gestured behind him. "We need to talk. Follow me."
Something about his tone inclined Hange to hold her tongue for the moment, and followed him. At first she expected him to take her to a more private location, and was surprised when he instead led her to the side entrance of the Scout headquarters, and stopped next to a small row of trees along the path.
Hange looked at him curiously. "What's up?"
Levi tapped his hipbox nervously. "I was doing some of my training exercises yesterday, when this happened."
Levi pulled out one of his blades, and the next second a black aura enveloped the blade completely like a second skin.
Hange's eyes widened. "Whoa, how are you doing that?!"
Levi shook his head, his eyes narrowed at the black blade. "I don't know. It happens if I concentrate, but if I stop…"
The blade slowly faded back to normal.
Hange frowned thoughtfully. "But what does that mean?"
"At first I wasn't sure, but then I tried using the blade with this...aura, or whatever it is, activated. And when I did…"
Levi held up the blade, and the black aura came back. He then swung the blade forward, and was able to completely sever one of the smaller trees just above the base of the trunk. The upper half fell to the ground with a heavy thud.
Hange's jaw dropped. "HOLY SHIT! HOW...WHA...THA…"
Levi nodded, his gaze fixed on the blade that had defied all known laws of physics.
"Exactly. I don't know what this is, but somehow I have this strange new ability. And I'm not the only one. Mikasa told me that recently her senses have unexpectedly gotten much sharper, and she's able to see and hear things much further away than is normal."
Hange rubbed her chin thoughtfully. "Curious. Perhaps it has something to do with the Ackerman bloodline?"
Levi shrugged. "Maybe. But considering all the strange things that have been happening lately, I'd be willing to bet it's connected to whatever caused that quake."
"Probably..."
As the weeks rolled by, things were further complicated when Jean started being able to emit the same black aura as Levi, and Sasha's observational skills also drastically improved, though not quite to Mikasa's level. Both of these rendered Hange's hypothesis about the Ackerman clan less likely, and lent credibility to Levi's idea that it was linked to whatever strange phenomenon had caused the quake.
Unsure of what was going on, in the end Hange decided that all they could do was try to make the most of these abilities, and so they began to train and hone them in earnest.
Before long all the Scouts and a good number of the Garrison were able to emit the same black aura and enhance their observational skills, though to varying degrees of success, and this allowed them greater control and power in combat and ODM gear training.
Hange was impressed by the results, and was naturally thrilled when she managed to pull both of them off herself, but it also made her nervous. If these strange new abilities were exclusive to Paradis, then they would have a distinct advantage when it came time to fight Marley again. But if Marley had also acquired these new abilities, then that would just put them right back at square one.
Still, until all the pure Titans were cleared out they couldn't do anything about the outside world, and so she tried not to dwell on it.
But then something happened that raised even further questions.
It was early in the morning, and most of the heroes of Shiganshina had gathered in Hange's office for a meeting before they began the day's work. The only one missing was Sasha, which wasn't unusual, as she was often running late.
Suddenly, the door to Hange's office burst open, and Sasha strode in with a young girl at her side.
"You guys!" Sasha practically shouted. "Something big happened last night!"
The other Scouts, which included Hange, Levi, Eren, Mikasa, Armin, Jean, Connie, and Floch looked back and forth between Sasha and the young girl with a mixture of curiosity and confusion.
Hange leaned forward, her interest piqued. "What is it?"
Sasha nodded. "We were gathering herbs in the woods near our house, when Kaya...come on you tell them. Don't be shy."
Sasha gently nudged Kaya forward.
Kaya looked at the Scouts nervously before looking down at her feet, her face slightly flushed.
"I...I accidentally turned into a Titan."
Everyone's eyes widened in shock.
"What?!" Armin shouted.
"What do you mean?" Levi frowned. "Was it a pure Titan?"
Sasha shook her head. "No, she was able to come out of the nape. From its appearance, and based on what was in Mr. Yeager's books, I'd say that she somehow obtained the power of the Cart Titan."
Jean blinked. "Huh? Does that mean that something happened to the last user of the Cart Titan?"
Armin frowned. "But this doesn't make any sense. If the user of the Cart Titan was killed, then the power should have gone to a random newborn Eldian child. Why would it go to her?"
Hange rubbed her chin. "From what his notes said, the powers are transferred through the paths by means that we don't fully understand. While this is unexpected, it doesn't seem impossible."
Hange looked down at Kaya and asked her kindly. "Is there anything unusual or strange that happened to you before you turned into a Titan?"
Kaya fiddled with her skirt, her face still rather red from all the attention. "Um...nothing recently. I, uh...I did eat a weird looking fruit a few weeks ago...but...no, I don't suppose that would have had anything to do with it."
Connie stiffened.
Hange chuckled. "Probably not. But a good scientist always keeps possible variables in mind."
Sasha looked at Hange anxiously. "You're not going to force her to join the military just yet, are you? I know she has the power of a Titan, but she's still a kid!"
Hange sighed. "We can't just ignore it, but I will do my best to make sure she isn't exploited. Since from what I know the Cart Titan was primarily a noncombatant type, I think we'll be able to keep her out of harm's way."
Sasha nodded. "Thank you."
As Sasha and Kaya left, Hange felt rather mixed emotions. She was of course relieved that they had another one of the Nine Titans, and that by extension Marley had one less. But at the same time it made her anxious.
Another puzzling mystery. What does it all mean?
After several more months had passed, the day finally came when the Titan guillotines appeared to have cleared out all the Titans. The Scouts departed for Shiganshina, both to survey the land for any straggling Titans, and to make sure that Shiganshina was still secure.
By the time they spotted Wall Maria, they hadn't seen any Titans, which was both reassuring and worrying, as whenever things seemed to be going well for them, that was when something unexpected happened. Usually something bad.
As they approached the wall, they noticed something odd.
Armin sniffed the air. "Is it just me, or is the air...salty?"
Eren sniffed the air himself before frowning. "No...you're right…"
They also spotted several large birds flying above the wall, and as they got a good look at them they realized it was a type of bird that none of them had ever seen before.
But the strangest thing they noticed was the inner gate. Just like the gate at Trost, it appeared to have been magically repaired.
Hange grimaced. Something unusual is happening. Perhaps we shouldn't go right into the district.
She raised her voice. "Soldiers, alter course!"
Instead of going straight for the inner gate, they instead headed for one of the corners of the district where it connected with Wall Maria. Once the Scouts reached the wall, they immediately used their gear to scale up the wall.
As soon as the Scouts landed on top of the wall, all of them, without fail, were utterly stunned by the sight before them.
Connie's eyes widened. "Whoa…"
Jean's jaw dropped. "Holy shit…"
Instead of the large land mass of grassy fields and dotted forest areas they were expecting, they found themselves looking at an endless expanse of water that stretched all the way to the horizon. There was only about a kilometer worth of beach separating the wall from the water, and they could see the tides ebbing and flowing against the shore.
They had reached the ocean.
"What the hell?" Levi said in bewilderment. "Did the rest of the island somehow get swallowed by the sea? Was that what that quake was about all those months ago?"
Hange looked down at the beach, her face a mixture of confusion and awe. "No...if that was the case, it would be a bunch of jagged cliffs jutting out over the water...but the shore looks smooth…"
"Look!" Armin pointed. "There's something in the center of Shiganshina!"
They turned, and saw the ruined district of Shiganshina stretched out before them. Much of the district had been destroyed during the battle to reclaim Wall Maria, while the rest was still in a state of ruin as a result of the many years of neglect that the absence of human life had inflicted upon it.
But towards the center of the district, right in the middle of the crater where Bertolt had transformed during the battle, was a large green cube.
Hange frowned. "I suppose we should investigate."
A short time later the Scouts arrived in front of the green cube. Up close they could see it was big enough that Eren's Titan would struggle to lift it, though Armin's could probably pick it up with relative ease.
On the front end of the cube was a large crystal. And inside the crystal…
Eren froze. "Is that…?"
The Scouts looked at the figure inside the crystal in disbelief.
"Ymir!" Jean breathed.
He reached out and lightly touched the crystal, and it instantly shattered, scattering fragments everywhere and depositing an unconscious and rather wet Ymir at Jean's feet.
Jean leaped back in shock. "Shit! I didn't expect that to happen!"
Sasha knelt down next to Ymir. "But...I thought she was dead."
Armin's eyes widened. "Look. There's writing on the side of the cube."
They looked up, and could see that he was right. All over the surface of the cube were what appeared to be strange markings at first glance, until they realized that they were actually words etched into the stone surface.
They stepped forward and examined it closely.
This is a message from the Founder Ymir to you, my descendants.
I am very familiar with the feeling of being trapped in a hopeless situation.
This is why I have used my power to free you from the circumstances that condemned you to being in an unwinnable position.
I have extracted everything on Paradis island within Wall Maria, and moved it to another, and very different, world. One with an entirely different history, one that is completely unaware of the power of the Titans and the Eldian race, and thus will bear you no hatred or ill will because of what your ancestors did.
As part of the process of moving Paradis to this world, I have adjusted the power of the Titans to fit into this world better, and in a way that will not require my help going forward. In this world there are mysterious objects known as Devil Fruits which, once eaten, will grant the user some kind of special power. The trade off is that the user can no longer swim, as they are cursed by the sea. Since this world is mostly covered in water, even more so than the one you came from, this makes the Devil Fruits a slightly risky power, but most consider it worthwhile.
There are three types of Devil Fruits. Paramecian, which alters the properties of the user's body in some way, Zoan, which gives the user the power to transform into some kind of animal, and Logia, which allows the user to become and control an element of nature. There are subcategories of each, and the rarest and most powerful Fruits are the mythical Zoan, Devil Fruits that allow the user to transform into a mythical creature. I have converted each of the Nine Titans into a mythical Zoan Devil Fruit power.
This means that each of the Nine Titans still retains all of the benefits and abilities they had, while the weaknesses and drawbacks have been reduced. One of these drawbacks was of course the curse of Ymir, something which you will be happy to hear no longer applies in this world.
Eren of course has the power of two Titans, and as of the moment you are reading this he has full access to both, and so can use the Wall Titans to defend Paradis if that should prove necessary. While this world is not inherently hostile toward your island like the previous one was, it is still a dangerous and complicated place, and you will need to be on your guard. But the focus of this world is not on you, and your chances of survival are significantly higher than they would have been in the other world. With that in mind, I wish you all the best of luck.
Oh, and because I was feeling generous I decided to resurrect my namesake and even let her keep the Devil Fruit variant of the Jaw Titan. I'm sure that will make Historia quite happy.
There's also armament and observation Haki, but I'm sure you'll be able to figure out about that on your own.
Best of luck, and farewell.
The Scouts stepped away from the cube, utterly stunned by what they had just read.
Levi shook his head. "Damn."
Pure joy lit up Mikasa's face, and she wrapped her arms around Eren and Armin, hugging them tight and crying tears of relief, knowing that they weren't going to be taken from her any time soon.
Hange rubbed her head, a bewildered smile on her face. "Well...good news, our fears and concerns about the world destroying us are now moot. Bad news, all of the intel Grisha provided us about the outside world is now useless, and we're now completely blind about what's beyond our little island."
Jean shrugged. "Still, based on what we know about the world we came from, and if what Ymir said about this world is true, that doesn't seem too bad."
Levi frowned thoughtfully. "She briefly mentioned something about armament and observation Haki. If I had to guess, that's referring to the strange new abilities we acquired several months back. I'm guessing Haki must be something that's fairly commonplace in this new world, so it's a good thing we have access to it."
Sasha's eyes lit up. "So that explains why Kaya has the Cart Titan! She must have eaten the Devil Fruit variant of its power!"
Hange nodded. "Yeah, you're right."
Connie raised his hand awkwardly. "Um...guys...I didn't mention this before, because I didn't think it was relevant, but...I think I have the Beast Titan."
Everyone turned toward him sharply.
"Huh?" Jean exclaimed.
Sasha gasped. "Oh! That weird fruit you ate at Ragako!"
Connie nodded slowly. "Yeah. I didn't think anything of it at the time, but…"
A grin lit up Hange's face. "So, that's another Titan power on our side. It'd be good if we could find them all. Well...I guess we'll have to go around and start asking people if they've seen and/or eaten any strange looking fruits lately."
Levi shook his head. "This whole thing is so fucking bizarre."
Mikasa tightened her grip on her two boys, tears of joy still streaming down her cheeks. "I don't care."
Armin laughed nervously. "It's also kind of exciting though."
Eren nodded. "Yeah."
Eren looked up and saw a pair of the strange new birds flying above them. As he observed the serene blue sky and smelled the sweet salty air, he felt at peace.
He didn't know what this strange new world would hold for them, but for the first time since they visited the basement, he felt optimistic about the future.
Author's Note: Surprise One Piece crossover! I think it fits for April Fool's, because while it's not exactly a joke chapter, the premise is quite a bit more outlandish than anything else I've done so far. I've seen a few other AOT and One Piece crossovers, but all of them just kind of awkwardly have the One Piece characters show up in the AOT world (or vice versa) with no real explanation, overlooking the fact that the two worlds are extremely different. So here I tried to have the two worlds colliding in as realistic of a way as possible.
This is one story I can confidently say that I will definitely not be continuing. For one, in order to really do the premise justice, the story would have to be nightmarishly long, and while I have a passing interest in One Piece, I can't say I'm a fan. I find the lore and the worldbuilding to be really fascinating, I think the concept of Devil Fruits is absolutely genius, and allows for a lot of very creative powers and fights. But while I've dabbled in the manga and the anime, neither really clicked for me, as the pacing is really slow (particularly in the anime) and I can't stand Luffy. And while I know a lot about the lore and everything, I am by no means an expert, as a lot of what I know comes from reading the wikis and watching Tekking101's videos from time to time rather than the original source material. I mean, I find his videos entertaining, and I find discussions about One Piece more interesting than actually reading or watching One Piece itself. I can definitely see why it's so popular, and there is a lot to admire and appreciate about it, but overall it's not really my cup of tea.
Still, if anyone who is a fan of One Piece wants to take this premise and run with it, be my guest. While I've left things fairly open, my idea was that Paradis was placed in the calm belt between the North Blue and the New World some time during the two year time skip. And with the Founding Titan Eren would have power that is more or less on par with the Yonkos, so there's a lot of possibilities. Would Paradis ally themselves with the world government? Would they join up with one of the Yonkos? Would they try to keep to themselves? What would happen if they met the Strawhats? Like I said, lots of different possible scenarios.
As for what happened in the AOT world after part of Paradis vanished, let's just say that several years later Marley would eventually discover a massive lake where the territories of Wall Maria used to be, and in the center of the lake would be another poneglyph and Annie's crystal, and the poneglyph would explain what had happened, and then also announce that the second they touched Annie's crystal all the Titan powers would stop working. I was originally going to write out that scene, but I was feeling kind of lazy, so I didn't.
Anyways, be sure to let me know what you thought, and stay tuned for more.