Koro-Sensei: Hah! It is to laugh. You'll be pleased to know that I haven't been idle. In between my teaching lessons, grading homework and evading assassination attempts, I've been covertly tailing you.
Saitama: (Thinks back to noticing a round-headed figure in the discount shopping mall before it ran off in embarrassment) I *thought* that was you.
Koro-Sensei: (Blushes) Yes, well, I tallied up my totals, (points to numerous pie charts) and reached an inescapable conclusion. (Pauses for dramatic effect) It is IMPOSSIBLE for me to conduct enough free time to do the amount of training that you did. You've had three years - I have less than one year.
Saitama: (Looks disappointed) So, what you're saying is that you didn't do any exercise at all.
Koro-Sensei: Grr. You-you-! (Composes itself) Anyways, during the course of my investigation, I decided to delegate my assignment to an expert who'd be more capable of giving you a workout than I possibly could.
Saitama: (Cracks knuckles) Sounds like an excuse to me.
Koro-Sensei: I think this opponent may actually give you a challenge, and maybe even give you that adrenaline rush you've long been seeking. I give you... Squirrel Girl! (Blares entrance music from several horns, tubas and vuvuzelas from underneath its cloak)
Squirrel Girl: (Enthusiastically) HI!
Saitama: (Politely) Hello.
Koro-Sensei: You may laugh at her appearance, but let me assure you that her ability is anything but!
Saitama: I wasn't laughing.
Koro-Sensei: She's faced off threats ranging from Dr. Doom to Thanatos to Galactus to Wolverine, and beat them all single-handily with no outside help or Deus ex Machinas to help her.
Squirrel Girl: Um, excuse me, but who's this guy?
Koro-Sensei: You don't know who he is??? He's taken out numerous threats, ranging from Drygar the Destroyer, to Abominus the Galactic Threat and Terminus the Terminal.
Squirrel Girl: I'm sorry, but I've never HEARD of any of these guys you just mentioned.
Koro-Sensei: Goes to show how effective he is. He has no reoccurring villains, since pretty much everyone he faces head-on never comes back for a rematch.
Squirrel Girl: YOU'RE still here.
Koro-Sensei: (Flustered) Okay, those he spares out of the goodness of his heart gain a momentary reprieve.
Squirrel Girl: Fine, out of sheer curiosity, I'll fight him for you. Still haven't caught your name yet.
Saitama: (Booming voice) They call me... caped baldy.
Squirrel Girl: Didn't quite catch that. Oh well, a little workout for 1000 Yen shouldn't be too much of a hurdle.
Saitama: You're aware that 1000 Yen is like 10 bucks where you come from? And there's a bounty on his head worth 10 Million Yen?
Squirrel Girl: (Turns to meet Koro-Sensei's guilty eyes) Really???
Koro-Sensei: (Trying to whistle inconspicuously and failing) Do you have any idea how much a teacher makes on their salary??
Squirrel Girl: Sounds like it'd be more profitable to go against you instead.
Koro-Sensei: Oh... Oh no! My secret science project has suddenly rebelled and backfired on me! Who could've seen this coming??
Classroom: (Thinking) Seriously?!
(Squirrel Girl launches a punch towards Koro-Sensei that is immediately blocked by Saitama)
Saitama: Not so fast. If you're going to fight this teacher, you've got to go through me first.
Koro-Sensei: (Has tears leaking from under his eyes) Saitama...
Saitama: (Turns head halfway around) Don't look so relieved. Once I'm done with her, I'm fighting you next.
Squirrel Girl: I don't understand - why are you going to so much trouble to protect someone who'll destroy the Earth?
Saitama: He's the only opponent who's managed to last more than five seconds against me. Besides, no matter how you look at it, he's human.
Squirrel Girl: (Peeks over at Koro-Sensei) THAT'S a human???
Saitama: Okay, he's a little taller than usual, but that's no reason to discriminate.
Squirrel Girl: I don't think height is the problem here...
(Squirrel Girl launches a series of punches, kicks and feints that Saitama easily dodges)
Squirrel Girl: You're pretty good, but how about THIS?! (Makes chittering noises) (Dozens of squirrels come swarming up around Saitama's body and feet)
Saitama: Hey... where'd all these squirrels come from?
Squirrel Girl: Impressive, isn't it? I can summon legions of squirrels to do my bidding!
Saitama: Aren't they terribly infectious creatures?
Squirrel Girl: (Waving hand, pointing finger in front of mouth) SHH SHH SHH!!! Don't let them hear that!! You'll reduce their cuteness quotient, and make them feel bad!
Saitama: It's not exactly a national secret.
Squirrel Girl: If you're going to insult my furry little friends, I'm not gonna hold back!
Saitama: I don't like being violent towards women. Especially women heroes. But if you insist...
(Saitama lands a punch on Squirrel Girl that causes ripples to echo out in the air behind her body)
(Squirrel Girl stands there looking stunned. The nearby squirrels are also looking on in shock. For some reason, Saitama also looks surprised)
(Saitama raises a single finger and experimentally pokes Squirrel Girl on the shoulder)
Saitama: You want to try that again?
(Squirrel Girl nods reluctantly)
(Saitama winds up a bigger punch, stronger and faster than the last one, sending it towards Squirrel Girl's midsection, resulting in an echoing sonic boom that rattles the windows in buildings in a 50-mile radius)
(Squirrel Girl stands there looking unaffected)
Saitama: Huh. That's really weird... It's like you're not even there.
Koro-Sensei: AHA! Just as I thought!
Nagisa: Uh, excuse me. Could you explain what's going on?
Koro-Sensei: Well, when I was conducting my surveillance on Saitama, I noticed an interesting contradiction. He was able to blow away apocalypse-causing threats with nary a sweat, but was completely defenseless against harmless animals. (See Rule #4)
Koro-Sensei: In short, he can only release his full strength against planet-destroying threats. And although he walks away from crippling blows with nary a scratch, he can be hurt by ordinary household pets.
Squirrel Girl: Well, it looks like you're at a severe handicap. How about you just give up?
Saitama: I don't have to hit you to beat you. (Punches the ground, sending boulders of turf and deep sedimentary rocks flying upwards, scattering nearby squirrels away)
(The squirrels having seen Saitama's strength up close have lost their will to fight and are running away as fast as their tiny legs can carry them)
Squirrel Girl: Don't be scared! He's trying to intimidate you! His punches can't hurt you! Just swarm all over him and -
At that moment, Squirrel Girl had a sudden premonition.If she forced her squirrel underlings to infect the strongest foe she'd ever faced thus far with their germs, she'd be going down a path of corruption from which there'd be no going back.A road of darkness that she'd constantly decried in the past, and would wind up becoming a hypocrite for daring to use an underhanded technique for the sole purpose of "winning" at all costs.
But would that cost be worth selling her soul for?
Squirrel Girl: Um, excuse me, but would you mind not voicing out my inner thoughts??
Koro-Sensei: Well, sorry, but not everybody is as fluent in squirrelspeak as you are. I'm just translating for the benefit of those who're wondering why you're just standing there.
Saitama: Well, all your squirrels have run away. There doesn't seem to be much point in us fighting anymore.
Squirrel Girl: I'm not done yet! I can still try to win against you!
(Squirrel Girl rushes against Saitama with her retractable claws, while Saitama futilely tries to punch Squirrel Girl with no effect)
Koro-Sensei: Uh-oh. I should've seen this coming.
Koro-Sensei: Squirrel Girl's power is to win against overwhelmingly powerful opponents that would otherwise never be beaten in a fair fight, while Saitama's power is to easily win against overwhelmingly powerful opponents with little to no effort.
Koro-Sensei: In short, their abilities cancel each other out. Unless there's some kind of buffer or handicap, this fight will remain a perpetual stalemate that'll never end.
Saitama: Look, there's no real point to this. We're not getting anywhere.
Squirrel Girl: I agree. It seems ridiculous to fight over a misunderstanding when we're not even having any fun over it.
Saitama: It must be nice to be thrilled at employing every single available resource you can get against overwhelming odds.
Squirrel Girl: Exactly, EXACTLY!! There's nothing like the rush you get from winning!
Saitama: And yet, you don't seem able to bring me that kind of euphoria you so warmly embrace. I'd love to be as chipper as you for winning all the time.
Squirrel Girl: Hey now, don't pout! I'll think of something. So, what do we do? Play Video Games?
Saitama: (Makes a face) Ugh, no. That's such a cop-out.
Squirrel Girl: Well, I don't feel satisfied without concluding our fight properly.
Squirrel Girl: How about if I wear a suit of strength-enhancing armour?
Saitama: Been there, done that. They didn't do much for me.
Squirrel Girl: (Looks over at Koro-Sensei) What do you know about that alien human over there?
Saitama: Not much, but there's loads of informational pamphlets out there. (Holds up trading card that has Koro-Sensei's stats on them)
Squirrel Girl: (Reads a bunch of footnotes and cross-referenced information in the margins) This is quite comprehensive for a national secret.
Saitama: I don't bother with that junk. All that matters to me is that he's smart and fast. Everything else is just noisy data dumps.
Squirrel Girl: (Walks in the direction of the school)
Saitama: Hey, don't get close to the schoolteacher.
Squirrel Girl: I'm not going to fight him. I'm going to use him.
Saitama: (Looks confused) Use him how??
Squirrel Girl: If you bothered to read your priceless card, you'd notice that Koro-Sensei can change his body at will, and can wrap around his students to protect them, serving as a wind-resistant suit.
Squirrel Girl: Sensei, how would you like to feel a young girl's body pressed against yours?
Koro-Sensei: (Looks pervertedly pleased) I'd like that very much, but you're not my type.
Squirrel Girl: Even better. I want to get inside you.
Koro-Sensei: Uh... shouldn't that be the other way around??
Squirrel Girl: There's a point to this madness. (To Saitama) Go ahead, try punching me again.
Saitama: (Shrugs, gives another wind-up and punch with similar wind velocity towards Squirrel Girl / Koro Sensei)
Squirrel Girl: I... felt that!
Koro-Sensei: Are you crazy?? You could've taken my head off!!
Squirrel Girl: These are my conditions if you want me to fight this guy. And I don't want some flimsy excuse like how you're suddenly allergic to squirrels.
Koro-Sensei: (Nervous) Funny you should mention that. *Cough cough* See? New weakness. I simply wouldn't be able to fight at full strength.
Saitama: That's fine with me. Oh, and if you try to do anything funny to Squirrel Girl's body, (does a mock sideways hook) I'll punch you.
Koro-Sensei: No - NO! This wasn't supposed to happen! You guys were supposed to fight each other, not gang up on me - NO! NOOOOOOOOOOOOOOOOOOOOOOOOO!!!!!!!!!!!!!!!!!!!!!!
The following Squirrel Girl / One Punch Man teamup Vs. Koro-Sensei has been censored for your consideration, since you would be overwhelmed by its awesomeness, leaving you feeling disappointed with any future fights for years to come. You'll just have to fill in the excitement yourselves.
The resulting aftermath is a schoolyard brimming with dozens of weird-looking alien instruments among a field of debris, and the two heroes fist-bumping each other while Koro-Sensei lies panting out of breath in a nearby field where despite his exhaustion, is still swiftly dodging his student's bullets and knives aimed at his direction.Squirrel Girl: That was fun! We should do this again!
Saitama: Well, you certainly lasted longer than expected. You must be feeling pleased with yourself.
Squirrel Girl: I'm just sorry I wasn't able to make you feel as chipper as I do.
Saitama: Don't worry, I have a little something planned later.
(Squirrel Girl leaves)
Koro-Sensei: Well, you must be satisfied with your little battle, so I'll be going back to class now...
Saitama: We're not done yet. I said after I fought her, you'd be next.
Koro-Sensei: But - but I just spent three hours dodging your attacks!
Saitama: I wasn't fighting you, I was fighting her. You just happened to be in the way. Now that we're all done warming up, let's get serious.
Saitama: Super Move Serious Series.