Author's Note

Welcome! Thanks for taking the time to check out my Attack on Titan/Godzilla crossover story! Before we begin, there are a few things I need to explain first in order for the story to make sense.

First, this is set in an alternate Attack on Titan world where a bunch of details about how the world operates, how the government and military are organized, and what the Titans are, are all different from canon. As such, I will not be adhering to the established lore in all aspects, though the general story structure, at least at first, will be similar to what we saw in canon.

Second, the 'Titan Shifters' in this story shift into monsters from Legendary's Monsterverse, instead of the usual Colossal Titan, Armored Titan, and so forth. They will be referred to as Alpha Titans. The regular Titans, however, operate just as in canon. That is, they're mindless humanoid giants that want to eat people.

Third, the MUTO monster from the 2014 Godzilla film is here referred to as Kiseiga, which is a play on the Japanese word for 'parasite', which is 'Kiseichū'. The name MUTO is very odd in my opinion since every other monster in those movies is given a regular name. This naming scheme is actually similar to what Toho did with the spider monster Kumonga (the Japanese word for 'spider' is 'kumo') and the praying mantis monster Kamacuras (the Japanese word for 'mantis' is 'kamakiri').

Fourth, while I'll be using the familiar characters from Attack on Titan, and will generally characterize them as they were originally, this will NOT be the case for every character, particularly Eren, who has several intentional differences from his canon counterpart.

Finally, I'm using the anime names for all the characters, so it will be Bertholdt Hoover, not Bertolt Hoover, and Armin Arlelt, not Armin Arlert. That's all for now, and I hope you enjoy my story!

Attack on Titan X Godzilla: Alpha Predator

Wall Maria. Fifty meters tall, and made of solid stone, it was an impenetrable marvel of human engineering. Stretching as far as the eye could see, ten-year old Eren knew that if one were to follow it for the hundreds of miles it extended, eventually, they would arrive back at the spot he was at right now. A gigantic circle, it was the outermost of three concentric walls that protected humanity from the man-eating Titans, which roamed the entire Earth outside of Wall Maria. As such, Eren knew that of the millions of people that lived within the Walls, he was one of the closest to the horrors that awaited on the other side. Sitting under a tree with his best friends, Mikasa Ackermann and Armin Arlelt, Eren wasn't thinking about that. Nobody ever thought about that. The sun was shining brightly, birds were lazily flying in the sky above, and Armin was reading from a book he had smuggled out of Shiganshina District.

The cage I call home. Shiganshina.

"They called it the Alpha Predator!"

Drawing himself out of his wandering thoughts, Eren couldn't help but laugh. "Seriously, Armin? Don't tell me you actually think that stuff is real. They're just stories made up to entertain children like us!"

Armin's expression turned defensive, but his tone remained enthusiastic. "Well, there's no way to know for sure, but wouldn't it be cool if it was?"

Eren scoffed, but Armin pushed on. "It says here that the 'Alpha Predator' was a giant reptilian monster with impenetrable scales and a roar so loud it could be heard from miles away! It even says it was 50 meters tall! Think about it, Eren!" Armin's eyes glimmered with excitement at the thought. "50 meters! That's as tall as the walls are!"

Staring up at the towering wall of stone, Eren felt an involuntary shudder run through his body. He knew why the Walls existed, but their everyday presence in his life was something he would never willingly accept.

I have the lousiest luck. Each Wall has four outcropping districts to attract the Titans, streamlining defense, and I just so happened to be born into one of them. I wake up every day surrounded by these Walls, while many people in the interior never even see them.

"That would be pretty cool," Eren admitted as he tried to mask his resentment at the world he lived in. "With it by our side, we could finally leave the Walls."

"Exactly!" Armin exclaimed with a bright smile, pleased that he had won his friend over. "Then we could finally see the rest of the world! Gigantic lakes filled with more salt than any merchant could ever collect! Plains of grass filled with all sorts of bizarre animals! Fiery mountains with liquid rock pouring out of them! Think of the possibilities!"

Eren couldn't help but smile at Armin's enthusiasm. "If it's real, then someday, you'll see it all. I'll come with you! While you're writing stuff down about everything we see, I'll hunt and forage for food. It'll be fun!"

"See?" Armin said with a proud smirk. "Nobody else wants to listen to me about this. Only you two. Yeah, the Alpha Predator's probably not real, but legends always come from somewhere. There has to be some truth to it!"

"I'm glad it's not real," Mikasa quietly said from her position a few feet away.

Eren rolled his eyes as he turned towards her. "Do you have to be like that? I wish it was real. I bet it'd help us kill the Titans!"

"How do you know it would help us?" Mikasa said, her stormy grey eyes examining the hot-headed boy she considered a friend. She subconsciously fiddled with the end of the red scarf hanging around her neck as she stared at him. "It might try to destroy us. Or maybe it'd help the Titans."

"You don't know that," Eren said as his voice started increasing in volume. "You're just trying to make us act all scared like you are!"

"I'm not scared," Mikasa said defensively as a dark look crossed her face. "I'm just being realistic."

Before Eren could start to get more heated, Armin stepped in. "It's just a story," Armin said, trying to calm his friend down. "It doesn't matter what we think a supposed giant monster would do. I'm just sharing some stories, you don't need to get all mad about it."

Eren's victorious expression slowly subsided. He glanced over at Mikasa, and gave her an apologetic look. "Yeah, I guess you're right. It just feels so unfair. We've spent our whole lives staring at these walls, wondering what it could be like on the other side. Besides the Titans, it can't be all that bad."

As the three children crossed through the gate back into Shiganshina District, they were stopped by the Garrison Regiment, as per usual. Eren grit his teeth and remained silent while Armin did the talking, exchanging pleasantries with the bored soldiers. It only took until they had rounded the corner of a building that Eren exploded.

"I hate those stupid soldiers! Always stopping us from coming and going, it makes me sick!" Eren kicked a nearby wall in anger as he ranted. Armin glanced at Mikasa, who shrugged her shoulders. Though she wasn't his brother, she lived with Eren and his parents, meaning that she had heard his rants many times before.

"Eren, they're just doing their jobs," Armin said diplomatically, trying to calm his friend down.

Eren shook his head furiously and started pacing back and forth. "That's the problem! They just do what they're told! They have access to the Military Police's ODM gear, so that means they could get to the top of the walls if they wanted to, but they don't!"

To Eren, the fantastical ODM gear used by the military represented the hopes and dreams of humanity. A contraption mounted to a person's waist, powered by compressed steam, it fired hooks which trailed long metal cables which allowed the user to travel through the air at break-neck speeds. Paired with a set of replaceable cleaving blades, it was the greatest tool humanity possessed against the Titans.

"It's been over a hundred years, and nobody's even tried to go farther than here! Eldia has remained exactly the same this whole time, even though there's a whole world out there, just waiting for us to explore!" Eren was getting even more heated than usual, and Mikasa started nervously keeping an eye out for any adults who might overhear them.

"Walls Sina and Rose both have gates at each of the Districts, but not Maria! Doesn't that bother anyone?!" Eren yelled, not caring who heard him. Mikasa glanced at Armin, silently telling him to shut Eren up, or she would.

"It bothered my parents," Armin quietly said. It took a moment to hit Eren, but when it did, a contrite expression crossed his face. Armin continued on, choosing his words carefully. "But when they tried going over the walls, they were eaten by Titans within an hour." Armin took a deep breath as he revisited the memory of that fateful day. "I remember when the Garrison Regiment came to tell my grandfather. The soldiers who were on top of the wall that day saw my parents die. They looked so uncomfortable with delivering the news."

Armin turned to Eren, his expression turning grim. "I want to leave the walls, Eren. I think everyone does. But we don't for a reason. It's for our safety. It may be unfair, but life isn't very fair. We just have to accept and go along with it. We can't do anything about it, so getting mad won't help."

Eren sighed. He hated to admit it, but Armin made a good point.

"You're right," Eren reluctantly said, his anger dissipating. "Just like always."

Mikasa looked satisfied. She shot Armin a grateful nod and tugged on Eren's shoulder. "We have to get home. Your mom didn't want us out too late."

"Yeah, I need to help my grandfather with dinner. I'll see you guys tomorrow at school," Armin said as he waved goodbye with a half-hearted smile.

"Yeah, see you," Eren said glumly as he turned and started off, leaving Mikasa to run after him.

"Eren, you need to control yourself. You weren't being very nice to Armin back there," Mikasa sternly told Eren as they neared the Jaeger home. She absentmindedly ran her hands through her hair as she waited for Eren's inevitable sarcastic remark.

"Oh, I wasn't being very nice to him?" Eren scoffed in disgust. "What, like how the Titans were to his parents?"

"I'm just saying," Mikasa continued. "He was really close to them, so you should be more considerate."

"He was close to them?" A brief memory flashed across Eren's mind, but before it could bring back his grief from a year ago, he shoved it back down and replaced it with anger, directing it at his friend instead. "Not like you would know anything about that."

Hurt filled Mikasa's expression as she turned away from Eren and pulled her scarf up to cover her face, leaving only her eyes exposed. "I told you. I'm sorry about what happened," Mikasa quietly said. Eren's expression softened for a second before he shook his head in disgust and took off running for his house as it came into view, throwing the most hurtful thing he could think of back at Mikasa.

"That doesn't matter! It's still your fault!"

Eren ran up the steps to his house and threw open the door, startling his mother as she whirled around from her place at the sink. "Eren! What's-"

SLAM!

Before she could say anything, Eren had slammed the front door shut behind him and bolted up the stairs to the roof.

Carla Jaeger sighed as she heard curse-filled yells filter down from above. A part of her wanted to go up and tell Eren to quiet down, but experience teaching him in class at school had taught her that it was better to let Eren wear himself out first.

The front door opened quietly, and Carla turned around. "Oh, Mikasa, nice to…."

Carla fell silent at the sight of Mikasa's tear-stained cheeks. Noticing Carla's stare, Mikasa wiped her face with her scarf. "I'm fine," she quietly said.

Carla walked over to Mikasa and knelt down in front of her. Mikasa stood still for a second, not wanting to give in, but quickly broke, throwing her arms around her.

"What did Eren say this time," Carla reluctantly asked. She hoped Mikasa would tell her Eren hadn't been the cause this time, but she was quickly disappointed.

"He said it's still my fault."

"Eren Jaeger!"

Eren winced at the sound of his mother's voice as he heard her open the door to the roof.

Great, I'm in trouble again. All the other kids don't have to deal with teachers on the weekends. Just my luck my teacher is also my mom.

"Yeah, Mom?" Eren called out, knowing there was no point in avoiding the scolding he was about to get. He cried out when he suddenly felt a harsh tug on his ear.

"Ow!" Eren yelped as his mother dragged him over the stone wall encircling the roof and forced him to sit down, kneeling in front of him to be at eye-level.

"Did you really say that awful thing to Mikasa?"

Eren avoided his mother's gaze, looking out over Shiganshina, wishing he were anywhere but here.

"Don't ignore me, Eren. Did you say it?"

Eren groaned in exasperation. "Yeah, because it's true!"

SLAP!

Eren rubbed his face as his mother glared at him. "You know that's not true. Don't talk like an idiot, even if you are one."

"I'm not an idiot!" Eren replied defensively.

"Then prove it! You know it wasn't Mikasa's fault, but you keep insisting on blaming her. She lost her parents, Eren. She saw them die right in front of her. She was nine, damn it. Try having some empathy for once, will you?"

Eren didn't respond, choosing to sulk instead.

Carla sighed. "Listen. I know how you feel. You're angry. You want someone to blame for the pain. I do as well. But Mikasa is not responsible for what happened. The sooner you accept that, and move on, the happier you'll be."

Grisha Jaeger shook his head as Carla told him what Eren had said to Mikasa. "That damn kid. I'll talk to him."

"Thanks," Carla sighed in relief. "Take him to the park, will you? I know he likes to climb the trees. I'll spend some time with Mikasa while you're out. I can tell her stories about her parents, that always cheers her up."

Grisha smiled. "You always were better with girls than I was. Still don't know how I convinced you to marry me."

Carla smirked. "It certainly wasn't for your looks. You could try wearing less dorky glasses, and maybe shaving for once."

"Ah, but where's the fun in that?" Grisha gave Carla a quick kiss before calling up the stairs. "Eren! Let's go for a walk!"

Grisha casually whistled as the park came into view. Really more of a grove of trees, Eren had always loved climbing the trees and pretending he was a soldier with ODM gear. Getting access to constant stories from Armin, whose grandfather was a bookstore clerk, had filled his young mind with a longing to join the Military Police and fly around with their signature gas-powered ODM gear. Grisha had to admit that he understood Eren's passion, but that didn't mean he was comfortable with it.

While the Garrison Regiment was responsible for the three walls, and the four outcropping districts that each wall possessed, the Military Police Regiment had jurisdiction over the vast lands between the walls, plus the capital city of Mitras at the very center of the walls and the many smaller towns and villages between them. They had a mixed reputation among the citizens of Eldia, despite being known as the inventors of the ODM Gear, which the Garrison had quickly adopted as well. Widely seen as corrupt and power-hungry, any time governmental reform came into discussion, they quickly shut it down. The Garrison wasn't viewed much more positively either, often viewed as lazy and incompetent. That didn't mean there weren't members of both who were good, however. Sub-Commander Erwin Smith of the Military Police Regiment, for instance, was well-known for being a proponent of creating a third branch of the military, the 'Scout Regiment' being its theoretical title. It would be primarily focused on exploring outside the walls, and several well-known figures, like Titan scientist Hange Zoë, and Captain Levi Ackermann of the Garrison Regiment, had publicly expressed their desire to join said military branch if it were ever created.

Grisha figured it was only a matter of time before the Scout Regiment became a reality. What concerned him was how unprepared Eldia was for what lay beyond the walls...and how likely it was that Eren would join such an organization.

"Why are we going to the park?" Eren suddenly asked.

Grisha chuckled. "Because you're in trouble, that's why."

Eren looked up at his father in confusion. "But I like going to the park."

"Oh! I'm sorry, we'll go somewhere else then," Grisha said as he turned around.

"No, it's fine," Eren quickly said, realizing his mistake when he saw his father smirk. "You're messing with me again, aren't you," Eren whined as they reached the park. He quickly jumped and grabbed onto the lowest branch of one of the trees, hoping to escape before the lecture began.

"Yep," Grisha said smugly. His expression then turned serious. "You are in trouble, though, and I figured I'd meet you halfway. C'mon, help me up."

Eren was surprised to see his father reaching up and grabbing a branch to pull himself up. "Uh, dad, what are you doing?"

"Climbing the tree, obviously. Come on, we'll chat at the top," Grisha said with a grin.

As Eren watched the sky turn orange from the sunset, he slowly began to open up to his father.

"She's always telling me off, acting like she's my older sister, but she's not! It gets on my nerves, especially when she tries to boss me around!"

Grisha shook his head in amusement. "By bossing you around, do you mean her suggesting you not start fights at school?"

"Well, she does do that, but that's not the point!" Eren replied defensively. He knew that his parents weren't comfortable with the absurd amount of fights he would get into at school, so he wasn't going to even try to defend himself in that regard.

"It just frustrates me," Eren admitted. "Out of nowhere, Mikasa just shows up and is always coming everywhere with Armin and I, and he always sides with her! Did we really have to take her in?"

"Yes, Eren. It was the right thing to do," Grisha responded patiently. "I know you blame her for what happened, but that simply isn't fair to her. If you keep bullying her about it, she won't want to be around you anymore."

"Good!" Eren said triumphantly.

Grisha rolled his eyes. "Eren. Besides Armin, do you have any other friends?"

"Well, no…." Eren began, only to be cut off by his father.

"Exactly. You're always picking fights at school, so nobody wants to be around you. I know you don't want Mikasa as a sister, and that's fine, but you could at least try being her friend. She's a good person, like Armin, and I think it would do you some good to be nice to her. She needs a friend, and so do you. Help each other out, will you? And definitely apologize to her as well. Whenever you're in the wrong, you should always apologize."

Eren stubbornly dug his heels in. "I still think it's her fault-"

"Eren." Grisha's voice took on a rare stern note, catching Eren's attention. "It wasn't. To continue to say so to her is cruel. If you ever tell Mikasa it was her fault again, I'll personally feed you to the Titans, you understand me?"

Eren sighed. "Yeah, I understand."

"Good. Let's get going. You're going to help your mom make dinner."

"What?!" Eren yelped. "I thought you weren't going to punish me!"

Grisha's eyes twinkled. "When did I ever say that I wouldn't?"

"I'm sorry about yesterday," Eren mumbled. Mikasa looked up from her lunch and stared at Eren while Armin shifted nervously next to them.

"I keep blaming you for what happened, and that isn't fair of me," Eren stated, clearly uncomfortable with admitting he was in the wrong. "I just got really angry, and I took it out on you. So….yeah. I'm sorry."

It wasn't the most eloquent apology, but for Eren, it was something. Mikasa smiled behind her scarf. "Thank you, Eren," she quietly said.

Armin grinned at the two of them, glad to see his friends getting along. A devilish thought suddenly crossed his mind, and he couldn't help himself. "Aw, Eren's apologizing! Wow, Mikasa, when are you guys getting married?"

Eren whirled around at Armin in shock while Mikasa blushed and sunk into her scarf. As Eren's outraged yells filled the air, Armin looked on with a knowing smirk.

I like to tease Eren and Mikasa, but they have no idea how grateful I am that they're my friends.

Armin's body slammed against the side of the building and he slid to the ground, tucking his head under his arms in an attempt to block the blows. It was the same group of kids that always seemed to end up picking on him. Usually, they would leave him alone when Eren and Mikasa were around, but his two friends had stayed late after school that day, leaving Armin exposed while he waited outside the school building.

It's my own fault. I just can't shut up about the outside world.

"Useless little Armin! You're lucky the walls exist, otherwise, you'd have died a long time ago!" As the other kids sneered at him, Armin groaned in exasperation. He felt the usual feelings of hurt start to make their way to the surface, but he swallowed bravely and stood his ground.

I'm not useless. I've survived worse than these bullies. I've lost people who cared about me. My mom, my dad...they always said to stand up for what I believe in.

"You're wrong," Armin said with a sudden surge of conviction. "There's an entire world out there, and someday, humanity will explore all of it!"

"Ha! As if you'll live that long!" Armin suddenly found himself picked up by the back of his neck and face to face with the leader of the group, who's malicious glare reminded Armin of the drawings of Titans he had seen. Cruel, and frightening.

"The world's a rough place," the bully sneered. "You're a bright-faced little kid who thinks everything will work out in the end. Someday, you'll end up trusting the wrong person, and you'll be dead in an alleyway!"

Armin wanted to cower in fear, but he prided himself on never backing down. "Don't you guys have anything better to do than threaten someone who dares to dream?" Just as he braced himself for another assault, he was suddenly dropped to the ground.

"Hey look, it's Eren!"

"Oh good, another one-"

"Wait, is that Mikasa with him?"

"Shit! Let's get out of here!"

Before he knew it, Armin found himself being pulled to his feet by his friends. "Don't worry, we got your back," Mikasa said as she glared after the retreating bullies.

"Thanks, guys," Armin said gratefully. Eren was already running after them, yelling at them to come back and fight. Armin looked at Mikasa and shrugged his shoulders, not surprised in the slightest.

"It's fine, Eren, let them go," Armin called out. "They're not worth it."

"I know," Eren growled as he stomped back to his friends. "Doesn't mean I don't want to kick their asses for attacking my friend. Look at them, running away from me like that. Pathetic!"

"Actually, I think they were running away from Mikasa," Armin corrected with a grin. "But thanks anyway. You guys always have my back. I really appreciate it."

Mikasa gave Armin a warm smile while Eren stepped forward and slapped a comforting hand on Armin's shoulder. "You're our friend. We'll always be here for you."

"So why did you and Mikasa have to stay late anyway?" Armin asked as the three of them made their way to the Southern Canal. Running north to south, and east to west, the canal system ran through each of the districts, meeting in the capital city in the center of Eldia. Starring into the clear water, Mikasa watched as fish lazily swam by, going about their lives without a care in the world.

"My mom wanted us to clean her classroom for her. She said she wasn't feeling very good, so she was going home early," Eren responded as he picked up a rock and tried to skip it across the canal. It sank into the water with a splash, not bouncing even once.

Armin perked up at the sight. "It's better if you use flat rocks, and throw them at an angle. Here, watch!" Armin picked up a rock and threw it into the canal. Instead of landing with a splash like Eren's, it knifed cleanly into the water and sunk to the bottom with barely a sound.

Armin groaned. "Well, in theory, that's how it works."

Mikasa calmly picked up a rock, and after a moment of deliberation, threw it into the canal. It caught the surface of the water just right and cleanly skipped across the surface, making it nearly halfway across.

Eren's eyes widened, and he turned to Mikasa with newfound respect. "Wow, that was actually pretty cool," he admitted. Armin chuckled at his surprised tone.

"Seems like I'm the brains, Mikasa's the skill, and you're….well…." Armin trailed off with a smirk, leaving Eren sputtering as Mikasa grinned from behind her scarf.

"Hey, I can do stuff!" Eren protested. "I can-"

The three children were startled by a bright flash of light, followed swiftly by a thunderclap. The ground shook for a moment, throwing all three children off their feet. Armin threw his hands over his ears while Eren grabbed Mikasa and drew her to him while he looked around wildly.

"It came from outside the wall," Mikasa said as she pointed to a trail of smoke coming from just south of the wall, right where a gate would have been if it was either Wall Sina or Rose.

Armin's eyes widened as a loud, mammalian roar emanated from the smoke's position.

"What the….what's that?" Armin wondered aloud nervously. Eren let go of Mikasa and started walking forward silently, as if he couldn't control himself.

Mikasa reached out and grabbed onto his arm, holding him back. "No, don't get closer!" Her voice was filled with sudden dread, like she knew something terrible was about to happen.

Around Shiganshina, all eyes were trained on the pillar of smoke, and everyone froze when a large head appeared over the wall. Covered in brown hair, it looked distinctly mammalian, with bright, intelligent eyes.

Suddenly, two bony tusks smashed through the base of the wall, sending chunks of solid stone flying across Shiganshina. With a jerk, the tusks tore upwards, raking through the wall like it was made of butter. In the gap that appeared stood a monster. While it looked vaguely like a mammoth, its body structure was more akin to a gorilla, with two massive front legs and two shorter back legs. Covered in brown hair, it lacked a trunk, but retained two long tusks sticking out either side of its nose.

The 60-meter tall monster would come to be known as Behemoth. And with its appearance, everything changed.

Author's Note

Thanks for reading the first chapter of my Attack on Titan X Godzilla story! Starting on Tuesday, I will be uploading new chapters weekly. Comments are always appreciated!
-AlphaBeta17 (4/24/20)