The Guardian Hero

Prologue: Sludge incident

Musutafu, Japan; 12:43PM

It was a really ordinary day in Musutafu, bustling and active, if you ignore the slight annoyance of heroes and villains fighting in front of media and crowds, enticing some shockwaves, explosions and loud noises. Well, not that those reached the back alleys or any roads that weren't the main streets.

In one of such alleys, a rather tall and bulky youth lazily made his way forward. Dark grey hoodie, black utility belt, light blue t-shirt, black pants filled with pockets and customized black military boots adorned his lightly swaying figure, him holding some groceries and sleepily grunting. It doesn't take a genius to guess the size of the youth's eye bags under those sunglasses and the degree of sleep deprivation, similar to a certain underground hero.

'Got some free time, only to bomb it with a great spring cleaning... Didn't think I worked that much that I needed a vacation. That's a miracle of itself, considering it's them though...'

His thoughts got cut short as smoke and explosions appeared some ways ahead, soon followed by shouts of panicked voices, making him take a run for it as his 'volunteer' work would require him to do.

After cutting a corner, he saw a slime based quirk user trying to possess an ash blonde teen that was firing explosions from his hands while fire and debris surrounded them, holding back nervous heroes to save and clean up while police backs off the media and interested crowd.

"I can't fit through these one lane streets!" said a giant lady.

"Fire based quirks are my counters, we need to wait for a right quirk!" said a man extending his hands as wooden branches to rescue people around.

"I'm too busy handling the fire, how's your side?!" shouted a firefighter hero.

"Hits and grabs aren't working on his sludge mutation and he's abusing the kid's quirk, we can't risk it!"

As our protagonist pulled a mouth mask and set the bag aside, he analyzed the situation.

'Great damage control, solid surrounding perception and a shit-eating lack of martial art knowledge due to reliance of quirks... Wait, that teen looks like Bakugo? Damn, always a troublemaker...'

He started running, achieving high speeds as he traversed across various surfaces to take a path in the blind spot of the sludge villain. Checking he'd reach it before it notices him due to the crowd's reaction, he kicked the monsters eye while drawing a dagger from his belt, cut near the hostage and pulled him out to safety in one swift sequence, stunning everyone slack jawed.

"YOU SON OF A..." it screamed...

"Noisy." A deep, lazy voice resounded as a concussion grenade landed by the evildoer's mouth, rendering it for several seconds as the youth stuffed it into a larger gas can and tied it with cloth for safety measures.

A circular shaft went flying as a popular figure popped underneath it, exagerrated muscles, casual clothes, golden hair with 2 antennas with a signature smile adorning his face.

"DON'T FEAR! WHY?! BECAUSE... Oh my."

"Fashionably late as always, giant beefcake." Reply silenced everyone again as nobody, to their knowledge, talked like that to All Might, who actually let a chuckle.

"Sharp tongue as always, huh. Long time no see, young Karna." laughed All Might, dropping another bomb, bringing up a wild frenzy.

"No way, the child hero...?!"

"Wait, who's that?"

"The youngest person ever to become a licensed Hero, at only 7 years of age, Karna!!!"

"Hold up, #5 ranked Hero who went underground 2 years ago?"

"Tsk, you and your big mouth, treat me to lunch after this mess." Sighed the now revealed teen Hero, patting the explosion user on the back to cough up and giving gas cans to a nearby policeman.

"That's certainly a deal, my friend." Agreed the American styled Hero, grabbing a paper and pen from his pockets, giving an autograph along with apologies to the student for being late.

"AUTOGRAPH!" shouted Bakugo, enticing a raised eyebrow from the casual teen Hero who got shoved the paper in front of him, with a whisper followed from now hesitant and shy previous talker "...please."

"Sure." Deadpanned Karna, signing the paper while laughing his head off in his thoughts after which he went back to pick up his bags.

After cleaning up and making sure the environment is safe, Karna lightly answered the reporters and evading sensitive questions, observing a green haired girl scolding the angry face ash blond boy.

"Katsuki-kun! Why did you run off with those two delinquents?! Look what you got involved in, making me worried!" shouted the girl.

"What, you're starting to sound my annoying old hag, will ya can it?! Doesn't take a genius to see this was a freaking accident! I'll give you a copy of this, so shut your piehole for the next week, got it?!" scowled the boy, showing the hero signed paper, knowing how to deal with the meddlesome girl, getting her eyes wide and filled with stars.

'Guess that bastard actually managed to raise her properly... Well, not like I have any business there...' thought Karna in passing, as he and All Might started to avoid the media and escape the scene.

Perhaps in a parallel universe, this accident would end up being known as 'Sludge incident' ending in complimenting and scolding 2 teenage boys. However, here it only got labelled as 'Return of Karna' which was one of many adventures in the young hero's hectic life.