Twelve years ago before superheroes rose to prominence in the world, there was one superhero that acted as the planet's protector. A young masked man that went by Sentaiman, who would act as the ideal fighter of justice that fought many monsters throughout the years.

However as those years went by, he became more quieter. Nobody knew what was going on in his mind as he fought with even quicker yet more brutal efficiency, yet he still fought for the side of good.

Until one day, he had decided to retire.

The world was in shock as their only superhero had disappeared from the public. Yet because of his retirement, the planet was in need of heroes.

And thus, the Hero Association was born.

XXX

The sun was shining, the birds were chirping and the weather was clear as A-City was bustling. The peace, while brief, had a pleasant feeling as everyone was on their merry way with whatever activities they had.

BOOM!!!

All that peace was gone once a huge projectile resembling a meteor had impacted in the middle of the city. The radius was quite large as the landing had caused the buildings surrounding it to be destroyed like doomsday.

Standing up from the smoking wreckage was a purple tall muscular humanoid. To emphasise on the extra terrestrial nature of this creature, it had a pair of antenna sticking out of its bald head.

Flying in the air, it began to throw many projectiles as explosions surrounded the city. The people were in panic as they ran for their lives from the incoming alien.

XXX

"Oi, brat! Where are you?!"

A man ran around the street, looking for someone. He was rather toned and stood at a fairly average height. He wore what a slacker would as he was a civilian. A hoodie, board shorts and a pair of sandals. However, there was something that made him stand out amongst the crowd.

He wore a sentai mask.

Many people stared at him with various emotions. Some looked at him with awe while others gave him looks of disdain. Why? Because they all knew him.

Just before he could make another turn...

BOOM!!!

Before he knew it, the city was filled with tremors as he felt his balance thrown off. Realizing that a monster was on the way, he began to realize one thing.

"Oh, no! Her parents are gonna kill me!"

XXX

A little girl who looked like she was about 10, was crying her eyes out in fear as the city was shook to the core. It all happened so far that she felt like she couldn't do anything.

Unbeknownst to her, the purple monster began to approach her. Slowly, it held a hand right behind her...

...before it turned into a large claw!

In an instant, the claw had clamped shut in a blink of an eye. The monster let out a small chuckle as opened it's hand, only to frown as it was left barehanded. Turning around, it saw a masked man carrying the girl in his arms.

The girl was sniffling as she looked up to see her babysitter.

"Sentai-san..." she muttered.

"Tch, brat. I told you not to run very fast," Sentaiman muttered as he gently placed her on her feet. "What if your parents find out you went missing? What would they say?"

The girl's cries began to die down. "I-I'm sorry..."

"Quite an impressive speed you have there."

Skull turned to see the purple monster approaching them. The girl looked deathly pale at the creature in front of them.

"Who are you? I'd like to know the name of the insect I would crush," it said.

"I'm Sentaiman. I'm busy right now, so I'll deal with you later," the masked man said as he turned back to the little girl. "Now, how many times do I have to keep telling you not to wander off?"

The little girl was silent, still frozen in shock from the monster. She gave out a whimper when she saw it looked even more mad.

"You dare ignore me?!" It roared, knocking the girl back on her butt. "I am Vaccine Man! I have arrived on Earth because of humanity's constant pollution of the environment! The Earth is a single living organism and you humans are the disease that is killing it with your germs!"

It began to transform into a much more bloodthirsty form with sharp teeth, bigger muscles and demonic voice becoming more apparent.

"The will of the Earth gave birth to me so that I may destroy humanity and their insidious civilization!" Vaccine Man roared. "Yet your dare ignore Earth's apostle?!"

It began to lunge at Sentaiman, having completed his full transformation. "Then indeed I must wipe humankind from existence!"

THWACK!

Vaccine Man was sent sprawling to the floor. Sentaiman's clenched fist was held out. Wordlessly, the masked man walked towards the fallen monster before grabbing a hold on one of his antenna. He raised his arm, lifting his head...

WHAM!

...before slamming it to the ground flat.

"You punk bitch! Don't you know it's rude to interrupt others when they're speaking?!" Sentaiman yelled while repeatedly slamming Vaccine Man's head into the concrete. "Earth's apostle?! Don't fuck with me!"

He finally let go of the antenna and walked back to the little girl, who had regained her collar back but still looked bewildered at the masked man.

"Anyway, If you want to walk around the city freely, then ask me or any adult that's close to you for supervision. Got that, brat?" Sentaiman continued as if what had transpired didn't happen at all.

The girl nodded without hesitation. Sentaiman turned to the groggy Vaccine Man.

"If you claim to be Earth's protector, you should be guiding humanity since they're the ones that live here. Not destroy it," he called out. "Seriously, destroying humanity just to save the planet. What backwards logic."

"Let's go find your parents," Sentaiman said to the girl as he led her away.

Vaccine Man watched them leave before a thought appeared.

'What kind of planet is this?' he thought before losing unconsciousness

It wasn't long before the Hero Association came in to capture the monster.

XXX

"Sorry it took long to take her back," Sentaiman said as he took the girl's parents back to her home. "We got holed up somewhere in A-City."

"Oh, dear," the mother said. "I hope the traffic wasn't too bad."

"It could have been worse," the masked man said as he took out something from one of his pockets. "Here."

The woman looked down at his hand. "A coupon?"

"They're having a free sale on beef," he said. "I thought that you might buy it for a family dinner."

"Oh, thank you but you didn't have to do that," she said, clearly surprised. "You could have took it yourself."

He shook his head. "I've been busy now these days. The job hunt has finally become hunting season now that there are poor saps out there joining the Hero Association."

"Oh, why don't you join?" The mother asked. "I hear that heroes make a lot of money there."

Sentaiman scoffed. "I'm looking for a stable job. Still, really appreciate the suggestion."

She smiled. "Well, would you like to stay for dinner?"

He shook his head. "I wouldn't want to impose."

She waved her hand. "It's fine. We have extra salmon and needed to finish it before the expiry date."

Sentaiman rubbed his chin. "How can I say no to that?"

XXX

It was night time and Sentaiman had returned to his apartment. Z-City was one of the most deserted areas in the world as it was populated by monsters known as mysterious beings. However, it was the perfect place to retire in peace.

Once Sentaiman entered his apartment, he laid on the tatami mat in exasperation. His apartment was rather small. The main area served as a living room/kitchen while the other two rooms were a bedroom and a bathroom. In the living room were a couple of cushions, a cheap television and a kotatsu.

His hand explored on top of the kotatsu before he grabbed what he was looking for. It was a newspaper, but on the front was a section of job listings. Sentaiman sighed as he went through the list.

There had been times when he regretted being a superhero. They didn't have any retirement benefits for sure. Plus, it wasn't a stable job since it interrupted him so much that it caused him to alienate himself from many people in his social life. And even if he did join the Hero Association, he was not going to work for a company that was far from heroic.

Sentaiman began to tick off several names. Twenty-three jobs and he had been fired in every single one of them. If there's one thing he enjoyed from his superhero days, it's that he had learned a variety of skills from themed monsters of the week.

A name had caught his eye. 'Supermarket Clerk'

"Well, it's better than nothing," Sentaiman said before circling it.

XXX

A/N: An idea where in the world of One-Punch Man, the most powerful superhero is trying to get a normal job. I'm trying to work on my comedy.