Grandpa Universe In Multiverse

Saitama went straight down to Earth and landed in the middle of a Demon horde. But, he noticed something.

These demons were very different from the ones he had been killing all this time. They looked too ugly and weak to him.

~Aren't these from Zulrak's army?~ he wondered.

*ROAR*

Soon he saw a huge one. It had a humanoid-shaped demon but just looked very big. It had horns on its head.

Saitama just walked towards it while beating the demons out of existence. He didn't even give them any thought and mercilessly butchered them. Eventually, he reached the large one. He jumped to the height of the head and punched normally.

*SPLASH*

The head got destroyed into a bloody and gooey substance. The demon also fell to the ground killing some smaller ones around it. But, Saitama was having a problem there. ~Why aren't there any demons that can speak?~

But luckily, while he was killing demons left and right, he finally saw something, not like a demon. It was a man, probably. In a futuristic-looking armour. He was also killing the demons left and right with his gun and hands.

*BOOM*

*BAM*

He left behind a trail of blood and dead bodies of demons as he went to the man. Soon, the man also noticed him but did not react to it.

Soon, Saitama was very close to him, so he spoke. "Where are the demons coming from? Where is their leader?"

But the man didn't reply and still continued to kill the Demons. Saitama being the impatient guy he was sometimes, moved very fast and killed all demons around a kilometre radius.

"Friend, I can help you destroy the demons permanently. I can help you destroy their whole realm. But for that, we need some communication." Saitama tried to communicate.

The man stopped moving and looked at Saitama for a while. As if assessing him. Soon, his suit made a noise.

"Scan complete. This man is a human, a powerful one at that." Voice said.

"A.I?" He asked.

"I am VEGA, the Artificial Intelligence who helps this guy here. He does not speak as his mind has been mutated by his rage and bloodlust for demons in the past tens of years. They call him DOOM SLAYER" VEGA explained.

"What happened?" Saitama asked.

"Some scientists messed up on the base on Mars and that opened a portal to these demon's realm. Since then, this guy here has been fighting them and getting stronger. They also killed his rabbits and he's angry." VEGA said.

"Hmm, I'm also hunting demons. I have travelled to a lot of worlds. Tell me where the ruler of this world's demons lives. I will kill them." Saitama firmly said.

"Good, their ruler is the Dark Lord. The Dark Lord is the title of the supreme ruler of the realm of Hell. We don't know what he looks like though." VEGA revealed.

"Take me to hell, then," Saitama demanded.

"Can't. First, we need to secure Earth. This guy won't go anywhere until then." VEGA said on behalf of the Doom Slayer.

"I will help. You go left, I go right. Kill all demons and meet me halfway." Saitama planned.

"Hmmm... deal," VEGA replied.

Saitama didn't wait and dashed to the right. Loud sounds of explosions came and slowly faded as he left behind dead bodies.

"Well, maybe let's meet at 1/5th way from this side," VEGA commented. After that, Doom Slayer also started slaughtering demons.

Saitama didn't take too long and killed all the demons in record time. In fact, all of these were so weak that even the speed at which Saitama was moving killed lots of demons around him.

So, he did just that and ran around at a fast speed. In just 15 minutes, he had done his job and now was on his way to meet the Doom Slayer.

"Oh, are you done? You are fast. That's fine. Follow me if you want to go to Hell." VEGA spoke.

Saitama followed Doom Slayer behind. He had no idea what was going on in the head of this guy. Eventually, they arrived in Hell with some kind of a portal. He didn't care to ask as he only wanted to kill demons.

"That big castle is where the Dark Lord lives?" Saitama asked the obvious. Of course, the big bad guy lives in the big bad castle.

"Doom Slayer, you kill the demons around here, meanwhile, I will deal with that Dark Lord. You just wait a second." Saitama said.

"How are you going to kill him? He is very strong." VEGA asked.

"Watch me," Saitama replied.

He kicked the ground and jumped a few metres high. Then, with decent force, he punched towards the castle.

With a roar, the punch travelled at a speed unimaginable. The demons around them were shocked too and even they looked toward the castle as if wanting to know their upcoming fate.

Then it happened, too fast for anyone to even react. Well, there were just demons but even they had the reaction of being scared already.

*BOOOOM*

An explosion that would make a nuke go shy occurred. The castle got covered in a cloud of dust and nothing could be seen to determine its fate.

"Huh..." That was the first time Doom Slayer showed an expression. It seemed he was happy maybe.

Saitama stretched his shoulder. He didn't want to wait any longer so he blew out air. It was nothing less than a storm. The cloud of dust got blown away, showing them the condition of the place castle used to be.

There was nothing.

Not even a brick left.

There was just a deep, wide and smooth crater. Even the sand had turned into glass due to the heat.

The demons around also got very scared. They tried to run away but Saitama sent some punches in all directions and killed them.

"Doom Slayer, I am on a mission to destroy the demon army of the biggest Demon King Zulrak. He wants to fight god and take his position. Do you want to travel with me and destroy these demons across the Omniverse?" Saitama asked straightforwardly.

~He's a bit different from Genos but I guess this will be fine.~ Saitama thought.

Doom Slayer didn't say anything, VEGA gave the answer.

"He agrees, but first, you need to help him kill every single demon remaining so they can never rise again," VEGA said.

Saitama lifted his hand to shake. "Deal."

Surprisingly, Doom Slayer shook it. So, they travelled all the dimensions known to Doom Slayer, slaying demons. They even destroyed the technology that connected hell with the earth.

Eventually, they cleansed the universe and went on their way to find another Universe with demons of Zulrak. Saitama had doubts that this world's demons were not related to Zulrak.

But, ~Any dead demon was a good demon.~

[A/N: Well, stating the obvious. This was the Doom universe. Too many people had requested this. Now, even Doom Slayer will help hunt the demons.]

[You can see Doomslayer on my Discord - .gg/DgHkrAn OR see them on Instagram - /mister_immortal_novel]

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