Chapter 33 - The Big Three
"Hah?" Katsuki let out.
Currently on his way to school, Katsuki had stopped on a dime just outside of it… because of a disembodied head which was seemingly merged with the floor.
"So… you're the student who won the First Year stage in the Sports Festival." the head muttered, "And a friend of Izuku Midoriya, that student turned vigilante."
"Yeah, now get the hell out of my way." Katsuki questioned, "I've got classes to attend, freak."
As Katsuki walked right past the head, it chuckled a little bit.
"Seems you've got spunk." the head noted, "Why's that?"
Katsuki paused for a moment, pissed off by the fact that he was asked a question which he shouldn't have to answer.
"Ain't it obvious?" Katsuki said in a raised voice, "You've gotta be a little cocky if you wanna be the best."
As Katsuki continued to walk towards his school, the lone head was left on his own.
"Seems he's quite the interesting one…"
"Welcome back from your internships." Aizawa stated, greeting his homeroom class, "With that formality out of the way… we can finally begin your real training."
"Oh, yeah! We're gonna be learning Haki, right?" Mina questioned.
"Hell yeah! We're gonna be the strongest heroes ever!" Kaminari exclaimed.
"Don't be so sure…" Aizawa noted, "Haki and its adjacent powers aren't something you can jump to so easily… for now, you'll merely be building up your talents so you can have a chance of using it in the future."
"How come we can't just focus on Haki right away?" Momo questioned, raising her hand.
"Because Haki is merely a way for you to amplify your physical talents. Even if you could miraculously use Haki right off the cuff, it'd be disadvantageous to you in the long run." Aizawa explained, "You'll begin to rely purely on your power advantage in comparison to your foes as opposed to creating well thought out strategies and learning to develop counters to your weaknesses on the fly, which means when you face your toughest opponents, you won't be ready."
"I see…" Momo noted.
"Even despite that, starting tonight, we'll have special, after school classes designed to teach you the basics of Haki, since the technique is one that'll probably take you years to learn." Aizawa explained, "Meanwhile, these typical homeroom and heroics classes will incorporate second and third year curriculum, but will mostly remain unchanged."
"So we just treat Haki as just a bonus then?" Ryuko questioned.
"Exactly." Aizawa stated.
Throughout the class, the less powerful students seemed… disappointed. After learning what Haki was, they believed it could be a way for them to finally even themselves out with their classmates like Katsuki, Shoto… or even the now departed Izuku and Chopper! It was... disappointing to hear that that kind of equalizer was being blocked off from them.
"I take it that some of you believe that we should focus all our efforts on Haki regardless, eh?" Aizawa said.
"Well, yeah." Sero stated, "It's an easy ticket to being stronger than anyone… even if there are some negative side effects, why wouldn't we want that?"
"Allow me to show you why your answer is wrong." Aizawa stated, "And introduce you to three Third Years… all some of the strongest students U.A. has had in years, known collectively as the Big Three!"
Walking into the room with an imposing presence, the three top students of U.A. Academy all walked into the room. One was a blonde male, and walked into the room jovially, one was a blue-haired female, and walked into the room with a graceful and dignified walk, and the final member was a purplish-black haired male, who walked into the room with a slouched posture.
"It's that guy…" Katsuki thought, recognizing the blonde as the head he had talked to earlier.
"Alright. Could you all give us a brief self introduction?" Aizawa asked, "Starting with you, Amajiki."
Through their own comedic means, both Tamaki Amajiki, and afterwards, Nejire Hado, both gave their own introductions. Read Chapter 123 of the original manga if you want to see that, as it's practically one to one here. ("woah, is that a guitar case? Do you play?" is something Nejire would say to Ryuko)
"I see you're all lacking in any sort of rationality…" Aizawa muttered in a disappointed tone upon listening to the socially anxious antics of Amajiki and the contrastingly extroverted questions Nejire shot to his entire class.
"Don't worry, Eraserhead-sir! After all, the main act is yet to come!" Mirio stated, referring to himself.
"These guys all seem like space cases…" Sato muttered, "Are you sure they're really the 'big three'?"
"Indeed… their personalities don't exactly suggest that…" Tokoyami noted, but before he, Mirio, Aizawa, or anyone else could say another word… a bold declaration was made before the entire class.
"You, Earthbound lookalike." Katsuki remarked, "Let's skip the theatrics… fight me."
At the bold, and possibly out of place remark that Katsuki had just made, the entirety of Class 1-A was completely flabbergasted.
"Dude! What the hell?!" Kirishima shouted.
"Such insolence!" Tenya shouted out.
"This is meant to be the strongest guy in the entire school!" Kaminari noted, "You can't just ask him to fight!"
"Oh ho… you're quite the energetic one." Mirio noted, "Sure, I'll fight you."
Yet again, the entirety of Class 1-A burst out in surprise at this.
"H-huh?!" Kaminari noted.
"Just like that?!" Mina added.
"Well… there's no way Mr. Aizawa's gonna let this slide…" Jiro reasoned.
"I'll allow it." Aizawa stated.
The class yet again burst out in surprise... a seemingly illogical scenario had played out right before their eyes, but unbeknownst to them, this is pretty much what Aizawa had planned the entire time.
Before anyone could even blink, the group was now in Gymnasium Gamma, the stage where Katsuki and Mirio were to fight one another.
"Mirio… you shouldn't do this." Amajiki stated, standing beside Mirio, fiddling with his hands below him to avoid eye contact with Class 1-A, "You're fighting against a single first year… this fight won't even make a good example..."
"He'll be fine… he's got some spunk to him after all." Mirio said while doing some stretches, "And he won first place at the Sports Festival, that's gotta mean something!"
"It's just like I thought… this guy isn't even taking me seriously." Katsuki thought, "His quirk likely allows him to put his body parts into the floor somehow… my best guess at the moment is that he can sprout duplicates of his body parts, but I oughta be ready for anything. This guy's confidence is off the charts, so it's not gonna be easy."
"This fight's gonna be so one sided…" Sero noted.
"There's… no way someone could be stronger than Bakugo, right?" Momo naively questioned, recalling how easily he beat her at the Sports Festival.
While the students of Class 1-A with limited fighting experience thought this, those who had fought against the Hero Killer had different thoughts due to the fact that they had been shown firsthand that the world was much wider than just Class 1-A.
"Don't be so sure…" Tenya interjected, "Aizawa may be pulling our leg, but if he's not… there's no way his title as one of the 'Big Three' is for nothing, especially considering Bakugo hasn't gained so much as a fraction of that notoriety after the Sports Festival."
"That blondie's confidence is through the roof as well…" Ryuko added, "Even I can tell he's pretty strong..."
"Alright!" Mirio let out, finishing his stretching, "Feel free to attack me whenever you want."
"Hmph… you sure you should be givin' that luxury to me?" Katsuki responded, confidently smirking as he finished stretching himself, "If you are... then DIE!"
Leaping towards Mirio with just his explosions to boost himself forwards, Katsuki used this opportunity to try and force Mirio to use his quirk… and as the third year's clothes began to phase through his body, and so did Katsuki's first explosion. The students of Class 1-A were embarrassed by the newfound nude state of Mirio.
"Sorry, it's tough to adjust my quirk for these clothes!"
"Tch!" Katsuki scoffed, "He phased through my attack without any damage, so his quirk must allow him to phase through stuff then… now let's test his limits!"
Utilizing an explosion behind himself, Katsuki shot himself back at Mirio, aiming an explosion at his back while the third year was fumbling around with his pants… but before Katsuki could do anything else, Mirio had vanished into the floor.
"He's vanished!" Tenya noted.
"No shit, einstein!" Katsuki angrily shouted, as he shut his eyes, "At the very least… he didn't instantly come back up when I was distracted… so he either needs time to prepare his attack, or-"
Before Katsuki could finish his thought, he instantly turned around behind himself and aimed an explosion at his opponent.
"He's got some fast reaction times… and some good intuition to boot." Mirio thought.
Despite that praise though, Mirio effortlessly phased through Katsuki's attack, and afterwards, aimed to narrow the distance between himself and Katsuki.
"But here comes the knockout blow!"
Mirio then aimed to stick his fingers into Katsuki's eyes, but before he could, Katsuki slapped his left hand onto Mirio's arm…. which went straight through it!
"A feint!" Katsuki noted.
Spinning around, Katsuki quickly realized that Mirio was attempting to get him into the perfect position where he could set up a finishing move… and once Mirio didn't react to Katsuki dodging out of the way, the bombastic student knew he had the advantage; Mirio couldn't see while he was using his quirk!
"Y'know, everyone tries to counter me that-"
"DIE!"
"Oh, he's good!" Mirio thought.
Before Mirio could launch his planned blow to the stomach on Katsuki, Katsuki launched a concentrated explosion below himself which aimed to cover the entirety of Mirio's body so that whatever part of him wasn't permeable would take massive damage.
Having been launched into the air after that explosion, Katsuki found his place on the ground a decent bit away from the smoke cloud, and began to shake his hands to get some sweat off of them.
"Welp… seems you guys were wrong." Sero said sheepishly.
"Yeah, Bakugo won in an instant…" Mina added.
"You idiots…" Amajiki thought, "If that's all you think it takes to beat Mirio… you're dead wrong."
After he had gotten some sweat off of his hands, Katsuki ran a decent bit away and prepared a non-lethal AP Shot with his hands. Just as the boy had predicted, Mirio leapt out of the spot that Katsuki had landed after he used his massive explosion; Mirio had seen Katsuki, and assumed that the first year would be cocky enough to believe that his massive explosion had KO'd the rather goofy third year.
"AP SHOT: AUTO CANNON!" Katsuki shouted, unleashing a volley of slightly upward aimed, low power explosions which Mirio narrowly dodged through permeation.
"That guy's technique…" Amajiki thought, taking a peek over at the fight between Katsuki and Mirio, "He's not just blindly firing explosions… all his movements are deliberate, and designed to end the fight in an instant… is this guy really a first year? He's scary…"
"What?! I thought he'd be knocked out from that last explosion!" Kaminari noted.
"Yeah! That explosion was massive!" Mina stated.
"It was powerful… but that wasn't the only point behind that attack." Aizawa stated, causing Mina and Kaminari to both look over at their teacher, "You get it now? Even if I taught you Haki, and you were ten times stronger than this guy… you still couldn't do a thing to him."
Not giving Katsuki so much as a moment to breathe, Mirio teleported out of the ground, this time a decent bit away from Katsuki to try to get around his superhuman intuition. Then, to get around his reflexes, Mirio tapped his feet against the ground and launched himself towards Katsuki's back at what had to be superhuman speeds.
Katsuki noticed this, attempting to use explosions to back himself up and dodge Mirio's blow, but it was a moment too late, as Mirio's fist had found a firm place in Katsuki's face, and was launched into the distance... at the very least, he had avoided most of the damage with his explosions, but Katsuki was still hurt quite a bit.
"That third year landed a hit!" Ochaco noted.
"Damn… Bakugo's playing right into his hand!" Kirishima commented.
"That's… it's slower, but it's still Shave!" Katsuki thought, now equipped with a bloody nose from Mirio's last attack, "Tch… it was too good to be true that nobody but me and that nerd knew it!"
(Side note: Yes, Mirio was able to utilize something akin to the Shave technique, much like how All Might was able to mimic the properties of Moon Walk or the Tempest Kick (air pressure attack) with his own super strength. What Mirio was using isn't one to one with the Shave technique, and was somewhat less effective, but it'd be ridiculous to say that the footwork behind the Shave technique hadn't at least been discovered and implemented into the world-class schooling that is U.A, albeit Shave and it's subsidiaries aren't widespread)
In the next moment, Mirio had yet again disappeared into the ground, as Katsuki was left to keep guessing just where Mirio would appear. Without a second to breathe, Katsuki was attacked from behind, and narrowly dodged by rolling to the side.
"Nice dodge!" Mirio said.
"Shaddup-" Katsuki began to let out, but it seemed that Mirio had used this to distract Katsuki, as Mirio was able to land a clean uppercut on the boy, afterwards returning to the ground, "O-only two hits… but my visions already blurring?! What the hell is this guy made out of?"
"Wow! Most people can only take one hit from Mirio!" Nejire chimed in from the sidelines, "Hey, Amajiki, that first year's really something, right? Right?"
"Mm…" Amajiki muttered.
Preparing his explosions in advance, Katsuki backflipped in order to dodge another, frontal attack from Mirio. The second he landed onto the ground, Katsuki unleashed an explosion to propel himself into the air, allowing himself to dodge Mirio's next attack before the blonde made it.
Even despite his dodges, Katsuki realized he was playing right into Mirio's hand right now, and was left with no opportunity to attack… Mirio's defense was virtually perfect, at least with where he was now. But, just maybe, if he could break his limits for just a moment… he could land a hit.
Katsuki shut his eyes, and keenly focused on his surroundings… as he tried to predict just where Mirio would show up.
"Focus…" Katsuki thought, landing on the ground as time seemed to stand still, and his surroundings seemingly vanished all around him… and then…
"An uppercut, straight below me!"
Leaping forwards, Katsuki avoided Mirio's attack before there was even a single indication that he would make it. Having just propelled himself out of the ground, Mirio had his quirk deactivated, and using the Shave technique along with his Explosions, which he had been hiding this entire time for this moment… this perfect moment, Katsuki was able to hit Mirio with a firm kick to the jaw… and it was a good kick at that.
"He got a hit on Mirio?!" Nejire said, shocked.
"A hit?!" Amajiki questioned.
Launched back due to the power behind the kick, Mirio quickly activated his quirk in order to phase through the floor, blocking any potential injury he might've gotten from rolling around the rough floor, afterwards popping up through it and landing on his two feet.
"Wow… I've really underestimated you." Mirio admitted with a smile, wiping some dirt off of his face.
"No shit ya did." Katsuki said with a smirk, "I could tell because of your expression… you were looking down on me."
"Yeah… I never thought that you'd realize that your quirk wasn't gonna be fast enough there." Mirio admitted, "And I never thought you'd be able to use that fancy footwork that sir taught me, you're really something!"
By that first line, beyond just the fact that Katsuki would have to waste time with changing his position in midair to get the explosions out of his palms, Mirio was referring to the inner workings of Katsuki's quirk. Basically, Katsuki's quirk allows him to excrete nitroglycerin-like sweat, which can then be lit up in order to cause explosions… but, how exactly can Katsuki even activate it?
"Yeah, my quirk factor wasn't able to keep up with how fast I wanted to go there, so I just had to ignore it." Katsuki said, "Seems I've still got a lot of training to do."
"Hm… if you're this strong, I get why Midoriya's got such a high bounty." Mirio noted.
"Don't play coy with that small talk of yours." Katsuki stated, "You're the best of the Big Three, right? I wanna see you at your strongest… and then blast you to hell!"
Mirio smiled, "So… you were able to realize that I was the strongest, eh?"
"It was obvious, just from the way you carried yourself."
"You've got some really strong observational skills…" Mirio said, "Okay then, I'll go all out."
Before Katsuki could even blink, Mirio was straight in front of him.
"This isn't gonna end well…" Aizawa muttered.
Jumping up into the air to dodge, Katsuki used his explosions to propel himself upwards. His aerial control was immediately compromised however, as Mirio quickly phased into the ground, afterwards popping himself out, launching up to Katsuki, and grabbing him by the leg. Instinctively trying to counter, Katsuki fired an explosion at Mirio's head, but Mirio threw Katsuki to the ground without so much as flinching, causing the first year to cough up blood once he hit it.
"He's too fast!" Katsuki thought, placing his palms on the ground and firing off of it so that he shot off in the horizontal direction. Making a swift landing, Katsuki looked around once he did… but Mirio had disappeared.
Shaking the sweat off of his palms once more, Katsuki awaited Mirio's arrival.
"Surprise!" Mirio shouted.
Without flinching, Katsuki reacted to Mirio's approach from not the floor, but the ceiling, as Katsuki leaped into the air with his explosions to boost him. Katsuki phased right through Mirio, but he was able to gain a suitable high ground advantage.
"He has to touch the ground again… so it's my win!" Katsuki thought.
And just as Katsuki predicted, Mirio fell through the ground once more… and so, he reacted accordingly.
"AP SHOT!" Katsuki shouted.
The explosion travelled rapidly downwards, and the instant that Mirio returned to the surface… Katsuki's plan to set up the entire fight had been revealed.
"PANZER MINE!"
Without a moment to react, the sweat that Katsuki had been gathering onto one concentrated spot on the ground throughout the fight (whenever he shook the sweat off of his palms) was detonated by his AP Shot, causing the very same explosive attack he had previously used on Best Jeanist: the Panzer Mine.
The explosion caused was a blast which rivaled the power of a Howitzer Impact in terms of both size and firepower; it was a blast that was sure to knock out anyone without a quirk which enabled them to be superhuman.
"Now that was a powerful move!" Sato noted.
"Yes… it appears that Bakugo set up that attack throughout the entire fight." Momo analyzed, "I personally found it quite obvious."
"Obvious... eh?" Mina questioned.
"Could… could Bakugo have won?!" Tenya questioned.
"That was my strongest attack I could use on him…" Katsuki thought, but before he could think anything else, he realized something, "Ah… fuck."
One firm uppercut to his jaw later, and Bakugo was knocked out by a now completely nude Mirio.
"Tch… figures." Ryuko scoffed, "The pervert wins."
"Yeah… while that last attack of Bakugo's was great, as Yaoyorozu said, it was quite obviously telegraphed. There's no doubt Mirio knew something was up, even if he couldn't tell exactly what." Aizawa noted, "Though that attack… it was put together quite well, and if they had allowed Bakugo to set it up, it would've probably defeated most of the U.A. faculty."
"Then… are you saying that Mirio's even stronger than the staff here, Mr. Aizawa?!" Kirishima shouted in surprise.
"Of course…" Aizawa noted, "After all… it wouldn't be farfetched to say that since All Might's retirement, Mirio is the strongest hero in the world."
"So… what did you all think of my quirk?" Mirio asked.
"That was too strong! How is tape supposed to compete with all of that?!" Sero shouted.
"Yeah! Phasing and teleportation, are you a hybrid, like Todoroki?!" Mina shouted.
"Hehe... well..."
While Mirio energetically explained his quirk to Class 1-A, Katsuki sat silently, bandages sprinkled across his various injuries he suffered in his fight against Mirio… the only reason he wasn't with Recovery Girl right now was due to his own insistence to not go.
"Not just being able to avoid any attack, but also being able to move wherever you want in an instant… that sounds like a really strong quirk." Tsuyu noted.
"It ain't that strong at all." Katsuki noted, "In power, my explosion completely blows it out of the water… it's him that's strong."
"Not to toot my own horn… but yeah, you pretty much got it." Mirio noted, "My quirk… it's strong thanks to the cultivation of countless hours of effort dedicated solely to improving it. Whenever I activate my quirk, I can't see, I can't breathe, I can't hear… the only thing that remains is my mass, so all I feel is a strange sensation of falling…"
"So then how were you able to know where Bakugo was gonna be throughout the fight?" Ochaco asked.
"Plain and simple: prediction… which is a skill that didn't come naturally to me." Mirio explained, "Without it, my quirk was weak… so much so that for my first year at U.A., I was practically quirkless… it was only at the tail-end of my second year after countless battles and training that I was even somewhat proficient at using my quirk."
"Just like Deku…" Katsuki thought.
"Your teacher told me that you all are going to be learning a secret technique of sorts which will make you all stronger than even me… but, as you've seen with your friend over there, natural strength and talent alone isn't enough to conquer any obstacle." Mirio stated, as he began to tap his temple, "You have to build up your experience as well… without that experience, you're useless. So grow stronger, and I have no doubt you'll all make fine heroes!"
From Mirio's speech, Class 1-A began to clap.
"What a tres bien speech." Aoyama said.
"It was quite well put together..." Shoji noted.
"Bravo! Bravo!" Tenya let out.
"Mirio's just as popular as ever…" Amajiki noted.
"Seems he had it handled on his own… was there even a point to us being here today?" Nejire pouted.
As Mirio's speech began to end, Mirio did a gesture to indicate that he was leaving now… but he felt a set of eyes on him like daggers.
"Explosion boy." Mirio began, "You could kill someone with that glare!"
"At the end of this year… I want a rematch." Katsuki declared, "I ain't gonna settle until I beat you!"
After Katsuki's bold declaration, a brief moment of awkward silence followed… and Mirio smirked.
"You have better things to worry about." he laughed, as Mirio continued to walk away. Katsuki merely watched on, frustrated that Mirio declined his invitation, yet not feeling as if he should say anything more.
Turning away to take the other exit, Katsuki began to walk back to Class 1-A ahead of the rest of his peers. Only Kirishima even attempted to catch up to him, as the rest waited for Aizawa's instruction.
"Yo, Bakugo, you good after that loss?" Kirishima asked, running to catch up to Katsuki.
"What? You think a little loss like that is gonna stop me?" Katsuki questioned, "Nah… I'm more motivated than ever."
While Katsuki retained the confidence he always had, it no longer held his signature arrogance which often accompanied it.
Stopping in place, Kirishima responded, "But… something's bugging you. We're friends, man, you can talk about it if you need to."
Katsuki paused.
"Something big is about to happen." Katsuki stated.
"Huh?" Kirishima questioned.
"Ever since Aizawa told us how Deku got his bounty, we knew that." Katsuki replied, "So I… so I gotta get stronger, otherwise, I'll just be an extra who needs saving. I don't have time to waste."
Not leaving so much as a moment for Kirishima to respond, Katsuki instantly continued to walk away… but Kirishima didn't let him, putting a shoulder on Katsuki's shoulder.
"Then we'll get stronger together… all of us." Kirisihima stated, "That way, we won't be in the way when that big thing happens."
Katsuki looked back at Kirishima, and merely gave a smirk and a scoff as his sole response, afterwards continuing to walk away.
In a white training room seemingly isolated from the rest of the world, a blue haired girl was training to ensure that her skills wouldn't grow dull.
Clashing against a Pacifista, the girl effortlessly dodged and weaved through every punch that the Pacifista attempted to unleash on her with exceptional finesse. It wasn't just punches either, as laser beams, auto-lock rockets, everything the Pacifista could throw at the girl was destroyed.
Lasers? Dodged with ease.
Rockets? Sliced in two.
Punches? Well... most were dodged, but with one in particular, the girl decided to block the punch with her sword instead of merely continuing her trend of dodging.
This punch completely stopped the Pacifista in it's tracks, almost as if it had hit a brick wall. The Pacifista still continued with unwavering dedication though, attempting to fire a laser at the girl before she could react, but the girl effortlessly leapt above the Pacifista and dodged even that. Flipping through the air with remarkable grace and beauty, for a moment, her sword turned black, as she slammed her hilt into the forehead of the Pacifista, causing it to fly backwards, and be defeated in an instant… all without breaking a sweat.
"What cheap toys." the girl commented.
"Lady Satsuki." the outlandishly tall disciplinary committee chairman, Ira Gamagori, began, having just entered through the door to the training room. Satsuki cast Gamagori a glance out of the corner of her eye, prompting Gamagori to continue, "Preparations for tonight's field trip are complete. All that's left is to address the students."
Returning her blade to her sheath, Satsuki Kiryuin turned back to face Gamagori.
"Very well." Satsuki stated, "Let us begin the hunt."
A solemn heel clack at the end of the traditional day for Honnoji Academy overpowered any other voice, as complete silence was demanded as soon as that noise sounded. The students of Honnoji Academy instantly realized what was about to come, as they paused their usual activites.
"ATEN… HUT!" Gamagori shouted, as from this singular shout, rows of bowing students began to form, all because of a lone heel clack... but it was no longer just that.
A blinding light appeared from the highest vantage point of Honnoji Academy, with the source being from a person whos voice reigned supreme at this school. The students attempted to catch a glimpse of the person who was at the very top, but the person would reveal themselves soon enough.
"Students of Honnoji Academy!" the voice belonging to Satsuki Kiryuin shouted, as the light around her seemed to dim due to her own overwhelming presence, "Today, you will be tasked with the extermination of the disobedient pigs who are impudent enough to not bend to our academies rules. Should you succeed in your mission, you will be granted a position as one of the Elite Four, and be granted a Three Star Goku Uniform!"
Letting out a noise of awe, the one-star students saw an opportunity to gain power and status, whereas two-stars saw an opportunity to prove their loyalty to Lady Satsuki and join her closest circle. One specific student in particular held a wide and devious grin on her face when she heard this.
"No Stars will not be allowed to come, but anyone else may..." Satsuki stated, preparing to say the name of the event, "FOR THE CULLING OF U.A. ACADEMY!"
As their mission was declared, the students of Honnoji Academy began to cheer for the incoming event... and as there was no more to say, Satsuki merely turned backwards to return to her domain… and prepared for the so-called… 'Culling of U.A. Academy.'
End of Chapter Notes
In regards to Mirio and his place in power scaling:
Yes, I would say that Mirio is stronger than Endeavor, Hawks, and Best Jeanist, though this may be changed as the story goes on. Mirio's biggest advantage compared to these three is that the latter group always had overpowered quirks with enormous potential. Meanwhile, Mirio was practically quirkless for his first and second year at U.A. Academy, forcing him to adapt to the curriculum in the same way that we see Ryuko doing. This, in turn, has caused Mirio to be in far more high stakes situations which forced him to evolve and grow stronger, whereas these experiences are few and far between for the rest of the top heroes. Even in MHA proper, the first time these top heroes experience any real challenge which they have to grow to overcome is the Hood Nomu... I'm not saying these heroes have just been off tending to their farms, they're still monstrously strong, it's just that Mirio has had an incredibly specific set of circumstances that made him really strong.
So, yeah. Mirio is probably the strongest hero in the world, but it's not by a large margin, and he's still far weaker than even a weakened All Might, or a USJ Nomu lacking Life Fibers.
This also makes it more clear power scaling wise why Katsuki lost to Mirio. Up to this point, Katsuki, Izuku, all of the U.A. students have been portrayed as incredibly powerful, with the top tiers of Class 1-A being shown as figures who put even Pro Heroes to shame... but, that's a big reason why this chapter is here: to show that even in the realm of canon, the students of Class 1-A are still just students who are horrendously outclassed by even just those in the Seven Continents; they still have a lot of growing to do, and the fact that they feel a sense of urgency to do so is scary.