Project Zero Mortals was a brutal campaign led by Goku Black and Zamasu to exterminate all mortal life across the multiverse, which unintentionally gave the duo an opportunity to directly observe all mortals. Throughout their expeditions, Black has seen all sorts of fighting styles from all sorts of mortals, such as a planet with sapient, carnivorous trees, a planet where every inhabitant stood as tall as an Earthling skyscraper, and even a near-extinct warrior race who have managed to surpass even the gods.

Although this universe held no lifeforms apart from the ones on this incarnation of Earth, it baffled the Saiyan at how much more diverse life on this version of Earth is compared to the 12 universes he was accustomed to. Mortal life scaled the entire spectrum from 'ghastly scum unworthy of life' to 'beings who should have been born divine instead'. Tomura Shigaraki already fit the former category, so it absolutely stunned the Saiyan when he met a mortal who was even more repugnant in the form of Hero Killer: Stain.

As if looking like a homeless, noseless ninja with a red scarf and raggy white mask wasn't enough, Stain had the audacity to lick the Saiyan's head! Black had seen all sorts of fighting styles, partially thanks to the humans in the version of Earth he originally attacked, but this was by far the most disgusting opponent he had ever faced. Having gauged the Hero Killer's raw power with a series of very light finger blocks, the Saiyan could conclude that even at full force, Stain had no hope of penetrating even his lips. In fact, even a good hit would be enough to kill him, like all other forms of life on this Earth.

In spite of such a massive power gap between the two, Stain could freely move whereas Goku Black was paralyzed with his right hand's index finger shielding his abdomen and his left hand balled up in a fist. To add to the gravity of the situation, the Saiyan recognized the black goo that was forming around him from his first visit to the Social Security offices with Jiro – the same goo that warped the sole surviving pseudo-nomu. Somehow, a mortal with no chances of surpassing the gods, managed to thwart one. Desperately trying to escape, Black grunted around the cold tundra of Hokkaido, which sunk himself deeper into the snowy ground, buying himself some time from the relentless black goo.

"I must say, it was quite a smart idea to travel to such a far away place devoid of human civilization," Stain commented, walking a few steps away from Black and then turning around to face the Saiyan's back. "An empty location such as this lets you use your full power freely without worrying about costs in damage. No one will know that you were even here in the first place. I certainly must commend you for such a location."

The Saiyan was still trying to power up, forming a small crater in the ground. Along with a barrier that came from the power up, Black was able to shield away from the clutches of the black goo to some degree.

"But, you should know that this location works well in my favor as well," Stain added on. "Hokkaido was an old training place of mine. The ice baths worked well to condition my mind and this is familiar territory to me. Yukikazahana Tundra, which we're in, has some strong trees and bears that helped morph my swordsmanship to be ready for the purge that you've interrupted me from."

"I'm not interested in listening to you being sentimental," Black growled, still grunting to the ground. The paralysis not only significantly hindered the Saiyan's ability to power up, but it even completely nullified his ability to fly. While his efforts in avoiding the goo were working, he was still a sitting duck as far as fighting went. "I want to know what…the hell…happened…"

"Now why would I, your adversary, tell you," the Hero Killer responded. "I do not owe you anything. Especially not what you did to help the vermin who have the audacity to label themselves as 'heroes'. "

These words reminded Black of his own rhetoric prior to meeting the Hottas. Back in his own multiverse, he used to think that Goku and Vegeta were rude and uncultured for not listening to his and Zamasu's ramblings about the superiority of the divine in comparison to the mortals. Now that he was listening to a mortal talk about the inferiority of other mortals, Black could understand the sentiment that his original adversaries felt.

As furious as the Saiyan was, the black goo around him grew more and more, starting to make its way towards Black's actual body. Despite the clearer advantage after powering up, the barrier and elevation change from the crater his power up formed were beginning to succumb to the enormous glob of goo. The Saiyan continued to grunt as he powered up, hoping that he would be able to brute force his way out of this predicament.

My voice is going to split if I scream for any longer, Black thought. Wait…I can scream? I was able to talk to Stain earlier, right?

The Saiyan stopped screaming and gave a smirk.

Clearly, his quirk must have something to do with paralysis, Black continued to deduce. It's quite a cheap trick: it does absolutely no real damage to me but it does certainly halt any attacks I can do. This warping technique from the fight with Jiro is clearly meant to bring me elsewhere, how clever. However, if it were a perfect paralysis, I would not be able to move a single muscle. Yet, I can talk, scream, and even flex my muscles while powering up…

Stain observed the black goo, piling up on top of the massive crater.

He should be gone any day now, Stain thought. It is a good thing that the bald prune and I were able to concoct such a plan to capture him; it is a win-win. Son Goku may not be a 'hero' but if he is able to be on such good terms with UA high, he will become one of those phonies himself. Yes, it's best to take out the roots of a weed while it is still fresh. After I finish my business here and in Hosu, I should come up with a way to deal with the League of Villains.

The ground rumbled, with the crater at the epicenter of this sudden earthquake. A large gust of wind blew the evergreens violently with snow flying from all directions.

"What the-" Stain spoke, startled by this development.

"KAIOKEN!" roared the Saiyan, breaking free from the black goo entirely. Although incredibly slow, he was finally mobile for the first time in a few minutes. For the first time in his career, the Hero Killer lost his aura of conviction. With his eyes widened, Stain was at a loss for words at the red light show Black displayed.

"But…how!" Stain yelled, completely bamboozled. "Not only should that lick have paralyzed you, eight minutes haven't even elapsed yet! I was told that your blood type was indeterminate! Could you have O blood type?"

"Now why would I, your adversary, tell you," Black said, mocking the earlier words of the Hero Killer. "Well, I suppose I will tell you anyway to set an example of how a generous god such as myself conducts with his opponents!"

"A generous god, huh," Stain commented, immediately losing the feeling of fear from before. "Once again, your power is truly second to none but the biggest weakness of a narcissist is themself. Now that I know this about you, there is no chance I can lose now."

"Such an unrefined way of speaking," the Saiyan replied, using the aura of the Kaioken to replace the movement of his arm to point at his foe. "But, no matter. I will not break my promise. I do not know what your quirk exactly is, but based on the information you have just said, I can conclude that your quirk paralyzes people upon licking them. The duration of this paralysis is based on blood type for some reason and it seems like the maximum time is eight minutes. However, if I was able to clearly speak, flex my muscles, and have full control over my facial movements, then clearly, this is not a perfect paralysis. All I had to do was create an artificial way to move, independently of my body. But as to why the quirk is based on blood type without using blood, I've got no clue…"

"That's actually quite genius," the Hero Killer complimented, feeling impressed at such a way to bypass his quirk. "The only thing you're missing is that my quirk used to rely on blood consumption to activate until recently. Now I can consume any bodily fluids for the paralysis to take effect, INCLUDING sweat. But otherwise, you are the first in my purge to have been able to genuinely bypass my quirk."

The Saiyan's pointing arm twitched slightly. The Hero Killer made a quick slash to Black's hair, trimming only large tips. Black's face scowled, realizing that he was not able to move his arm fast enough to block this most recent attack.

"Even with your newfound movement, I still have the speed advantage," Stain continued, holding the tiny strands of hair. "You have somewhat bypassed my quirk, something that I must commend you for. You've even shielded yourself from the warp goo, allowing you to prolong your battle with me. However, not only am I still faster than your current pace, your arm also just twitched. It seems like your 'divine genius', if we're being generous, failed to overlook how taxing this 'Kaioken' is on your body. Not only can you barely hold that arm up in the air, but you weren't able to move in time to dodge me. In fact, I was able to snip off parts of your hair, showing that your technique doesn't offer perfect protection. All I simply have to do is outlast your Kaioken and lick your hair strands every few minutes and you will be the one who is defeated."

Black scowled at this observation. Unfortunately for him, he never had much practice with the Kaioken beyond his bout with the brown giant during his first few days on this Earth. The Kaioken blessed him with the ability to move again but it was straining his muscles considerably. He really had no idea how the North Kai of Universe 7 was able to develop such a self-inflicting technique.

"Any pain dealt on me is worth it, especially against you," the Saiyan yelled, slowly raising his left arm to a fist at Stain. "All the noble heroes who were killed or injured fighting you, do you even know the effects of causing a genocide is, let alone a hero genocide!?"

He then leapt towards Stain with a punch, who was able to dodge the direct hit. The shockwaves of the punch leveled a large hill, sending chunks of it flying into the starlit sky of Hokkaido.

"Genocide is an ugly word, Goku," Stain replied, licking the sweat from one of several strands of hair he was able pluck from Black's head. "I would ask you why you are so protective of hero society but then again, you've only been exposed to the concept of a hero somewhat recently, have you? Your escapades have made UA High, Pro Heroes, and the police very interested in your abilities, so much so that they clearly aim to groom you to be yet another poster child serving no one but themselves."

He then threw several kunai knives at the Saiyan, which only caused Black's clothes to tatter.

"What in the actual hell are you talking about!?" Black screamed, powering up again while pieces of cloth ripping away from his shirt. "I've seen heroism firsthand around here. Eraserhead held out as long as possible so that his students would not be attacked during the USJ. The UA faculty rushed to the scene to make sure their students were alright. Even All Might himself fought for them with all his might!"

"Fine, I'll take your word for it," Stain responded, momentarily making Black confused at such a sudden change in reason. "But tell me, how many heroes have you seen in action besides this event? Let's use Present Mic, as an example. An English teacher, hero, DJ, and a podcast host in one person. These are all full-time jobs in their own right; is he really trying to help the lone citizen being attacked by villains or is he trying to build his own brand?"

"I was next to him in that booth during the Sports Festival!" Black answered, still trying to power up in addition to his Kaioken. "That's because…of…grrr…"

Although the Saiyan ended up prioritizing completing his power up rather than answering the Hero Killer's question, he couldn't help but admit that Stain had a genuine point in that question. Outside of the USJ, he couldn't recall any of Present Mic's hero activities since he first arrived.

"You see it everywhere nowadays," the Hero Killer continued on his rant. "A hero does a photoshoot for some modeling instead of evacuating a burning building. A hero signs a contract to endorse some cheap candy instead of stopping a thief who stole from a cash register. Two entire hero agencies play a game of baseball instead of saving a frightened child's parents from dying miserable deaths…"

Stain, teary-eyed, jammed his katanas down into the ground despite the growing wind and debris accumulating from Black's power up. He bent down on one knee, collapsing his body to the ground.

"Mother…Father…" he said. "I'm sorry I can't be like our Symbol of Peace, All Might. Not especially when such FILTH known as HEROES still roam the streets!"

He then punched the ground in anger, reminiscing of his childhood. In a moment of emotional vulnerability, the Hero Killer let a few tears flow down from his eyes.

"KAIOKEN TIMES 10!" the Saiyan roared, glowing even more crimson than before. He immediately leapt at the Hero Killer at a faster speed than before, performing the same type of punch from his first attempt.

This time, not only did his punch cause an even bigger shockwave than before, creating a crater that completely blew away most of the remaining plant life, the Hero Killer was also swept away by the wind, being tossed over 80 feet in the air.

I should let him die right here, Black thought. A mortal being able to do what he just did to a god is certainly worthy of the most capital of punishments!

As Stain fell down along with all the snow, the Saiyan considered the Hero Killer's arguments.

But, I can't make a dent in any of his arguments, Black assessed. He still rubs me the wrong way but his arguments have led me to believe-wait! No! This is EXACTLY what Aizawa warned me of in that car ride to the Sports Festival! The idea of 'false heroes' being spread to the mass public! Am I being convinced by him? No, that would be impossible. Unlike everyone else on Earth, I have no concept of a hero society such as this. Perhaps there are certainly other layers and perspectives that I haven't considered after all.

Black used Instant Transmission to Stain, holding him in a princess carry before descending to the ground and carelessly tossing Stain's body down, all while maintaining the Kaioken x10.

"What…" the Hero Killer said. "You – saved my life?"

"I still think that you're scum, unworthy of life," Black replied. "I've clearly bested you but I believe that you still hold some insights to this strange world, mortal."

Stain laughed, spewing up some blood while laying down on the snow.

"Still going on with that god-complex you have," the Hero Killer said, smiling. "You could have easily killed me in the air or even just let me fall down. Yet you spared me, clearly because you must realize there was some truth to what I was saying, is that right?"

The Saiyan chose not to respond to this question, collecting the curiosities that he formed from that fight. One such curiosity was that when Stain grieved his parents, he compared himself to All Might. Instead of intense hatred and rage at this hero, he displayed intense adoration and rage. Such a different perspective on one hero had to be explored.

"I also heard you mention All Might," Black said. "Even you think that he's deserving of the Symbol of Peace, huh?"

"He's the only one who truly cares," Stain replied. "Every act of his is done out of selflessness, he truly works nonstop for the benefit of society, and his fame is the only one out of all the heroes that I can say is well deserved. But unfortunately, no one in our society, not even Endeavor, is anywhere close to a hero as him. So you see, this purge is not simply the slaying of phonies, but also the revitalization of heroes who care just as much as All Might. And until the day he kills me, I'll keep fighting, even against you!"

The Hero Killer tried to get up but was stopped by the Saiyan's telekinetic force pinning him down.

"You did not answer my question from earlier," Black stated. "I asked you 'do you even know the effects of causing a genocide is, let alone a hero genocide?' Clearly, the extinction of all current heroes, minus All Might, is what you wish for. When I slaughtered mortals across other universes, I was under the impression that I was helping the universe be more at peace, away from random mortal conflict. It is very much like how you believe that slaughtering all heroes in Japan will lead to a wake up call and let people know more about the loopholes in our society."

"What the hell are you talking about, killing mortals," the Hero Killer said. "I'm not dumb enough to buy your fictional genocide just so you can pretend to relate to me! And I already told you where my conviction lies!"

"I literally blurted out that I am a god," the Saiyan said. "It's not like anyone's going to believe you anyway. Who would people rather believe: a maniacal serial killer responsible for the most deaths since All Might's reign, OR a humble cat café employee who happens to know how to react in a bad situation?"

Black then stepped on Stain's belly, who was still restrained by telekinesis.

"When Project Zero Mortals went astray, I was sent here, much to my displeasure," Black continued to ramble. "I was once even stronger than I am now, so I've been trying to make attempts to train despite your planet's puny power level since. But along the way, I met people who helped feed me, shelter me, and keep me off from becoming a crook such as you; turns out, those people were the same mortals that I despised not too long ago!"

He then telekinetically slammed Stain lightly to the ground.

"I admit, I cannot refute you about heroes being negligent on their duties," the Saiyan continued. "But just as society believes that All Might is the Symbol of Peace, somewhere out there, someone has their own hero as their own symbol of hope. And not everyone's hero has to be the absolute pinnacle of heroism. You may not see yourself as a villain, but you will certainly do a villainous act by extinguishing the one flame of hope that someone somewhere looked towards."

The Saiyan felt Stain's quirk wear off, allowing him to safely turn off the Kaioken x10. He then opened his hands and gave the Hero Killer just enough energy to move. The adrenaline running through his body made him forget about any aching his use of the Kaioken would do to his body.

"Don't even bother," Black commanded, noticing Stain's continuing aggression. "I've broken down your techniques entirely so you literally have no hope of beating me anymore. That black goo clearly is not your doing so clearly, you're working with someone else."

"I'm surprised you haven't asked about who sent me," the Hero Killer said, wobbling on his feet. "I assume you know about the League of Villains, correct?"

"What about them?" Black questioned. "I can guess from that pseudo-nomu in Hosu, it was you and the League's doing, correct?"

"Well, I suppose that's no surprise," Stain said. "But you don't know much about their leadership, do you?"

"It's just Tomura Shigaraki, is it not?" the Saiyan pressed further. "Isn't it just him and that inadequate mist portal?"

"Not quite," the Hero Killer added. "Tell me, have you ever heard of the fabled legendary villain who's existed since the first generation of quirk users, All For One?"

Author's Note: And there's another chapter much much sooner than my previous publication time! Stain is a pretty pivotal character in the franchise, so it's only right for me to wrap up the fight soon!

As for the treatment of this fight, it is VERY dialogue heavy. Some of you guys probably expected a full-on brawl with Stain and Goku Black but I find that impossible based on these two characters and their powers.

From Goku Black's side, he only needed one good hit to end the fight. However, his paralysis prevents him from fighting effectively, forcing him to unleash the Kaioken, a technique that he's only ever done against Gigantomachia in chapter 6. Gigantomachia is definitely a stronger opponent than Stain but Machia has no 'cheating' ability that would really hinder Black in any way. The way I envisioned the Kaioken being used here, it's like using the aura to move rather than your actual muscles. And of course, higher multipliers of Kaioken would increase Black's speed in this very specific instance. With Black's inability to access Super Saiyan Rosé (for now!) and his lack of real practice with the Kaioken, his only source of mobility until Bloodcurdle wore off, leaves him with very limited options in comparison to his previous fights in the MHA verse.

Dragon Ball characters, despite being absurdly powerful, have a tendency to be careless (e.g. Goku Black and Zamasu in the original timeline were blinded and coughing from a human gas attack. Even Goku Black got knocked off his chair by a bullet while having tea with Zamasu!) So having Stain be able to lick Black's head doesn't seem too far-fetched to me, especially with how confident Black got when assessing Stain's raw power in the last chapter.

On Stain's side of this fight, I think it's pretty clear that in terms of raw power, Stain is probably the weakest main villain Black has fought. However, Stain is also the first major human villain he's fought for an extended period of time (the chapter 2 villain duo don't really count), which makes him more intelligent than both Gigantomachia and the USJ Nomu. I think Black has a lot of immunity or supremely high resistance to any energy-based attack, however, I don't think Bloodcurdle is energy based at all, which would still make Black be stunned, no matter how strong he is. Of course, having Stain make Goku Black bleed, who still has all the durability he had when he was terrorizing Trunk's timeline, would make Stain EASILY the strongest character in the MHA verse. So I bypassed it by having Stain's quirk evolve from his canon version. Based on the explanation he provided in this chapter, as well as the intro sequence of the previous chapter, you guys can probably guess what happened to his quirk. Stain pretty much never had a chance to defeat Goku Black in a raw fight but by being able to paralyze him from ingesting sweat, as well as having another party transport Black elsewhere, it's pretty much as good as it'll get for him. Goku Black is a lot more cautious than his canon counterpart, especially since the scythe incident in chapter 1, so he will not willingly let the black goo quirk warp him to somewhere he has no knowledge of.

There are certainly other questions as well, such as 'Why not have Kurogiri warp instead?' or 'Why did Goku Black reveal that he's actually a god to Stain?' Well, I aim to have those answered pretty soon, guess you'll have to keep reading!

And that's a long note but thanks for reading! Mashing together two fictional universes can be a bit sensitive at times so I feel that this explanation was very necessary. But hopefully I can crank out another chapter at a reasonable date!