This is my first story in Fanfiction so please forgive me for my bad grammar and spelling errors,i'll try my best

to create an awesome crossover story between 2 of my favorite animes and I mean One punch man and Attack on Titan.

This story will take place after season 1 of attack on titan and while Saitama fought God from the fanmade on youtube btw

i doesn't own One punch man or Attack on titan not even the fanmade on youtube,really amazing fight tbh anyway without further

details here we go.

Chapter 1 (New World)

In one punch world after the death of Garou by God

Saitama was ready to attack God once more with serious series move this time since his normal punches didn't work on him he said "Should I get a bit more serious?" but when he land on his feet God spoke loud and clear "Poor creature. You will be exiled to another dimension so you won't be able to stand against my plans! To me you are ant!"

Then God extended his hands and stardust was gathering together in the middle of his chest making some kind of light ball but Saitama was not afraid at all, instead he was getting excited to see what this attack was about to do. The Caped Baldy was hoping for a challenge from this so called 'Godly Being' The only time he was getting a warm up was only the time he fought lord Boros.

God's pov

'He is indeed powerful for a third dimensional being his not one to be underestimanted but now it's over he will be gone from that dimension this instant!' He though inside his mind and stared back to his now fused light ball. If he had a face he would smile at the bald hero by now.

"Begone creature, your entertaining was quite enjoyable." Saitama was about to reply to him but suddenly the light ball was sucking everything inside. It was like a black hole, but Saitama didn't know what was happening and he didn't care either so he got pulled inside that light ball God had created against him then... Black, only black just like a space except there was no stars. Saitama felt like he was flying for a mere seconds.

But then the colors came back. Noticing he was falling from the sky. "Oh I see the ground."

The Caped hero landed with his red boots on the ground making a crater from his high momentum.

"Where am I? Damn this God dude was kinda annoying, just like telemarketings and why are you giant people naked?" He calmly asked them but with no response there was two titans front of him.

The first was 8 meters and the other was 5, both titans tried to eat him.

With no effort at all the hero dodge them easily, and with only one punch he turn them both to shreds.

"One punch again, how lame." He said while he was picking his nose with his right red glove.

Saitama's pov

'After I killed those two naked people a big Wall to the horizon grabbed my attention so I decided to go there and ask for information of how I can get back to city Z before the bargain sale was over. I didn't defeat that God guy though, but I don't seeing him around. Maybe he got bored and left...Crap I totally forgot about Genos I hope he is okay and got fixed by now. I remember him, he was into pieces from that 'God' poor disciple.'

When Saitama reached outside of the giant Wall he simply just jumped.

Reaching the end of it and seeing the edge of where he was before.

That Wall had cannons on it and he questioned himself.

'Why these people had those on a giant Wall? Maybe they was at war or something.'

Little did he know when he heared a shocked voice from behind him on the Wall with him.

"How the hell did you do that!?" He turned around with a blank expression on his face and what he saw was not that Strange.

It was a young looking girl, she was wearing a red scarf around her neck, dark brown long boots, a sleeveless light brown short jacket with a weird symbol on both sides of it and on front. The symbol looked like blue and white wings crossed together.

She also had a weird looking device that was having some blades on it, and it was attached on her legs, it was almost reaching her waist but Saitama's expression remained the same, calmed and neutral.

"Hey answer me!" Saitama ran out of his thoughs and face her "Oh, hi." The hero greeted her with his neutral expression still on.

"Can you just answer me how the hell you jumped all the way up here!? I just saw you and what's up with your dump outfit!" Mikasa was now grabbing his chest with anger and frustration.

"Woah don't torn my suit I don't have money to pay for a new one. I can barely buy some cabbage from the bargain sale so please let go, I'll tell you if that low your temperature down."

She let go and waited his answer with interest planted on her face. "I just jump from down there up here."

Mikasa was now way more angry to that stranger she was having front of her. She thought he was clowning around and his suit was one more evidence to support her point.

"Who do you think you are?! And who you think you are making fun of baldy!? Tell me the truth!" She shouted front of him so loud that her saliva covered his face but he still had the neutral expression.

He cleared her disgusting liquids from his face and then he finally spoke "Ah gross. And hey, what if I'm bald!? You got a problem with that!?"

His face was angry and stupid at the same time. "I don't care about that baldy I just want to know how you accomplished something that to humans are surely impossible!"

The hero was now getting Mikasa's point he had to give a different answer so she can believe his words.

Just like his hero training regiment. Unfortunately he knew if all the people around here was just like her and like all the others he met in the past, then they were surely going to ask how he got his powers. "Im just a guy who is a hero for fun, and my name is Saitama."

Mikasa's pov

'This baldy came out of nowhere, I literally saw him jumping all the way up here with no effort. As I see on his face he looks bored?'

'I gotta find out more about him and inform it to Eren. Maybe he is not from around here... Wait could it be what Armin was telling us about that giant lake called ocean? Could it be possible that this baldy was coming from there? I must find out mor-.'

"Hey, Mikasaaaa!" Armin shouted.

'It's Armin... I saw from the other side of Wall Rose and he wasn't alone, it was Captain and Eren with him. Without a second thought I said loud to them.'

"Eren, Armin, Captain! You need to see this!"

"Ohhh they flying :D" Saitama's expression turned into one of excitement, maybe he could have some fun here in this new world he was in after all.

They landed and Levi was the first one to speak. "Mikasa who is this individual?" Levi said with a calm expression. "His name is Saitama but what he just did well you won't believe me if I tell you so..." She turned to Saitama.

"Can you do that again baldy? Go down and jump all the way up here again."

"Saitama was just right why you had to call me baldy again?" Saitama was getting a little triggered and itchy everytime she was calling him baldy, but slowly he was getting used to it cause many other people in the past called him like that, and yes he still remembers the green sassy child calling him multiple names than just baldy like 'Tennis ball' 'Octopus' 'Avocado' 'Boiled egg' 'Goblin' etc. "Fine I'll do it." Everyone was watching the hero with widen eyes.

"Does he have a death wish or something!?" Eren said as Saitama now jumped down and returned atop of the Wall just to show them what Mikasa was trying to tell them, but his expression had turned from an excited one into a boredom one once again.

"You saw me now yaaaaay what now? I hope you won't ask me to punch something cause if i do i'll kill it with one punch like i did with the previous 2 giant naked people."

They was all shocked and staring the Caped Baldy with awe. Everyone wanted to know how that guy did this with no ODM gear equipped and what he was saying was surely sounded like nonsense to them but that picked Levi's curiosity.

"You saying to us that you can take down everything in one punch and you even killed 2 titans im assuming cause i agree they are naked and giant just like you described them." Saitama raised an eyebrow to Levi and answered.

"These naked people attempted to eat me. They was surely hungry."

Eren shouted with anger while he gritted his teeth. "They are NOTHING COMPARED TO HUMANS! THEY ARE BRAINLESS BEASTS THAT DEVOUR HUMANS LIKE YOU AND US!"

Saitama didn't paid much attention to Eren and ask. "Look can you tell me where is the closest road to city Z cause I'm going to miss the sale."

No answer, everyone was shocked and confused. They was trying to believe what they saw. A yellow suit with white cape guy just jumped down the Wall Rose and then he did the same thing to come back up!?

"You must come with us mister Saitama." Levi replied to the hero after he snapped out of it and indeed he was the only one to snap out of it first. Him then it was Mikasa and after the other 2.

"Oh? okay." Saitama simply said back to him and followed them. He jumped down from the other side of Wall Rose and he was running right behind them.

"Captain Levi are you seeing this!? He can keep up with our speed by just RUNNING!" Levi turned his head back and there was no doubt, Eren wasn't lying.

The guy was right behind and waved at them while he was running. "We will take him to Erwin, he will know what to do with this... guy."

When they arrived

"We are here" Levi replied to them as they landed and reached the HQ. "Okay Mister Saitama, you will answer me some questions I have for you later, but now you need to talk with someone else."

Saitama was watching his surroundings and didn't recognize anything of it. Medieval houses? Giant Walls? Fountains? Two things was sure in his mind. He was not in his world and most importantly he missed the sale.

Commander Erwin sat in his office while he was reading several documents, then there was a knock from the door.

"Come in" he said whilst he saw Levi and a weird bald guy came into his office. Levi explained to him Saitama's amazing speed and unimaginable power.

He even said to Erwin about the titans he faced and took them out in one punch! "Hi I'm Saitama and I'm just a guy who is a hero for fun."

Erwin pov

'I'm was sitting to my chair when I heared a knock from the door. It was Levi and with him it was a guy that was wearing strange yellow clothes and a big white cape. He seemed not to be from around here, but then again Levi told me things that it was hard to believe about our new possible allie that was front of me, so I decided to have a word with him personally in my office right now.'

"Levi leave us alone please." 'He did as I ordered him to do. After that I'm was alone with this Saitama, then I started the conversation.'

"Please take a sit." 'I said to him and he sat front of my desk.' "From what I have heared from Levi you must be really powerful my friend, but the situation here is not as easy as you think it is, let me explain you everything."

'He nodded his head to me so I could continue.'

"For years humanity was trying to reclaim it's lands from the titans from inside the 3 Walls but with no sighs of succeeding. I'm also informing you that humanity is living an extinction caused by the titans, that's why we builded these 3 Walls to protect humanity from the titans. Wall Maria. Wall Rose and the last one where is safer Wall Sina."

"Humanity have 3 forces so the cadets can choose which one they will join, but most of them joining the garrison regiment or the military police to be safe from the titans inside the Walls, but those who were brave enough joined the third one called survey corps. We are the ones that risk our lifes out of the Walls to reclaim what is ours. Our lands."

"Thankfully with the great power of Eren Jeager turning into a titan we successfully captured the well known Female titan, and her name is Annie Leonhardt. Unfortunately she is not in the condition to confess to us any information about her plans, if you want to know more about her you can freely ask Captain Levi, but that's not all."

Saitama kept in his mind the question about that Annie girl so he could question Levi later about it.

"We have found a route to the Shiganshina District which is where we will uncover the secret of the titans origins. With Eren's titan power and your unbelievable strength we might be able to reach the District without any trouble whatsoever." Erwin continued determined.

"Five years ago countless of innocent people lost their lifes cause Wall Maria had been breached by the Colossal and the Armored titan. I have fate for what Levi told me about you. Saitama, you and Eren Jeager are the only hopes humanity have remained against the enemy. You are humanity's last sparks of freedom and hope." 'I said to him and waited for a possitive answer.'

"So you need my help to reclaim your lands and save humanity from those titan things?" "Yes." Erwin calmly retorted back to the Caped Baldy.

"Fine, I'll do it. I'll help you get back what is yours cause I'm a hero and as a hero I must help those in need." Erwin planted a small smile on his face.

"Excellent, from now on you will be a member of the survey corps and I'm sure with your powers your reputation will grow very fast, and the rumours about you will be true and known to all humanity." Saitama was scratching his chin. "I don't do this hero job for admiration but because I want to!"

The Commander kept his smile and shake his hand with Saitama's right glove. "Of course you do and of cou-" He cut him off to say something. "If you want me to wear one of the outfits I saw the guys and the girl wearing earlier forget it." Saitama responded and continue.

"My suit remains, and the cape." He said with an idiotic expression planted on his face.

"Alright, your survey corps team will be with Captain Levi, Eren Jaeger, Mikasa Ackermann, Armin Arlert and our section Commander Hanje. Now you can proceed to leave. Captain Levi will show you your room, surely you need some rest."

"I'm hungry, can I get some food?" Erwin nodded to Levi while he came inside the office and pointed Saitama to come out, but the second he was ready to walk out of the door Saitama shifted his head back to Erwin.

"You sayed something about a Colossal titan and an Armored one 5 years ago huh." Erwin stoop up from his chair.

"Exactly, these 2 titans was the causation to lose thousands of lifes when this incident happened. Humanity is still fearing that day and wishing it would never come back again and that's why I see hope inside Eren Jeager and You, with both of you humanity will escape from the darkness once and for all."

Saitama's face turned into a serious one while shadows covered his eyes. "I promise to you, while I'm in this world I won't stop till I find those 2 titans and stop them."

"From the world I came from I'm was fighting monsters ten times bigger than those creatures you call titans, and much more stronger. Sure they were all weak and I killed every single one of them with one punch but if I compere them with those titans then the monsters was WAY more stronger."

Erwin found his words very interesting. "Can't you tell us a bit more about your 'world?' I want to know where are you from my new companion." Saitama yawn and put his hands up from the lassitude.

"Maybe some other time cause now I totally need some sleep." Then he left the office and he followed Levi to show him the way to his room.

That was the first chapter I hope I didn't make tons of mistakes, anyway thanks a lot guys and girls, let me know in the commends if you liked the story or not and I'll see you soon, I promise I won't abandon this crossover story till it's finished! Peace to everyone!