This story isn't as big of an influence as the first four, but it deserved to be mentioned as it is very good and should get some credit for what it did inspire

Viridian by SilvermistAnimeLover

Once Izuku had managed to calm Osamu down he asked the boy if knew anyone that would like help learning anything, the boy said he would get his friends and ran back into the building, he waited a few minutes before Osamu and a small group of six his age followed him out of the building.

Izuku introduced himself as Deku-Sensei and led the group to the veranda then went on to help them with their math, science, and spelling. He enjoyed teaching them and Izuku probably loved teaching kids the most because they always had questions.

When the four hours of teaching were done Izuku promised to be back to help Osamu with finding someplace to get his E.M.T training sometime next week, Izuku began packing up his stuff once the group had left to return to their respective apartments, he was about to leave but noticed that Osamu's father was leaning against the veranda still clearly waiting for him.

"Oh, do y-you need something still... Um," Izuku paused, realizing that he never got Osamu's last name or the man's name either "Just call me Zuki kid." The man interjected, tossing the butt of his cigarette on the ground and crushing it under his foot, then he walked over to him "Listen I don't have much other than the bastard," he commented rubbing the back of his neck.

"Seeing him like that ain't exactly something that happens every day either, so let me give you some advice." Zuki said then stared down at him with a very dark look.

"If you know what's good for you, you'll stay the hell out of Yokohama." Zuki sternly told him "W-what?" Izuku stuttered back shocked at the man's sudden turn.

Zuki rolled his eyes "You may be sheltered for a two-toes but I'm sure you know there are places that two-toes like you just can't go, right?" He responded and Izuku nodded, remaining silent, he knew some places banned quirkless people whether they were open about it or not, he had even been chased out of a shop once when he was six and didn't know better.

"Well unless you want to disappear off the face of the earth without any trace that you ever existed, you stay the fuck out of Yokohama." Zuki warned, pointing a finger menacingly at Izuku making him audibly gulp "You'll learn sooner or later that there's a reason two-toes like you should just keep moving." He added ominously.

"W-what do you m-mean?" Izuku asked voice trembling and Zuki scoffed "You're no dumbass, brat. Haven't you heard of the story of 'He who takes'?" He questioned and Izuku highly believed that it was rhetorical since he seriously doubted that anyone in this day and age didn't know of that story.

"He who takes" was a quirk-era boogeyman and there were probably many similar stories in different countries, it was only natural that with the rise of quirks that scary stories of someone who could take them would pop up eventually, Izuku could even remember being thrown jabs about He who takes being the reason he was quirkless when he was younger.

"Well old wives' tales like that always have a speck of truth to them, and let's just say that two-toes that are around He who takes have always had a way of... Disappearing. You understand what I'm saying?" Zuki asked, "I-I think so." Izuku muttered back and the brunette nodded to himself "Good. Cause if you break the bastard's heart by being stupid and sticking your nose where it doesn't belong, I'll find some way to bring you back and kill you myself, two-toes or not." The man threatened, glaring down at Izuku before he went to the apartment building.

Izuku feeling rather confused and nervous by the surprise confrontation scurried back to his hotel to finally check-in, but even after he had dinner and a talk with his mom Zuki's words stuck out in his mind, his travel plans didn't include going to Yokohama this time around but after what he'd said Izuku might never go there.

He wasn't sure if he believed that 'He who takes' was the reason behind all the disappearances of quirkless people, but he could easily believe that Yokohama could be more dangerous for a quirkless person than other places in Japan.

However, Izuku did pause to consider the idea of someone having a quirk that could take another person's quirk, he had seen people occasionally discuss the topic, but it was always quickly dismissed before any real discussion of the possibility could be held, they gave a lot of reasons but each of them sounded more like excuses to him.

Because Izuku thought the ability to take quirks would be very possible, there were plenty of quirks that could bend or break the laws of reality, and there were quirks that could copy other quirks or affect another person's quirk, so he didn't understand why so many people were adamant it was impossible.

He considered that it might have to be something to do with him being quirkless, Izuku was well aware that the 'scariest' thing of He who takes was that he could take your quirk but that clearly was an empty threat for someone quirkless like him, sure Izuku knew that the person could have any number of terrifying quirks, but the man's greatest threat was in a way, disconnected from him.

With that in mind, he didn't understand why He who takes would want with someone quirkless because what would there be to gain from someone quirkless? Izuku supposed it would only make sense if you took the smaller subset of stories that spin 'He who takes' being able to give and take quirks instead of just taking them, said variant was a bit harder for Izuku to believe but still in the realm of possibility.

But that wouldn't explain why the quirkless just disappeared if they got quirks by making deals with the "Devil" and why would quirkless people be told to avoid him? Maybe 'He who takes' just kills them but why? What would anyone gain from killing a bunch of quirkless people because wouldn't that just be a waste of time?

Full of questions about the old story he decided to look into it online because it wouldn't hurt to be a bit more informed about it, of course, there were a few places that briefly spoke about the story or the nursery rhymes of 'He who takes' but actually finding where the story came from was proving to be very difficult.

Izuku was admittedly frustrated when he found a fourth paper about how the story "could" have started and nothing about how it did, not even something benign like confusion over a quirk that would have been like Eraserhead's, he was about at the end of his rope so he did something he normally wouldn't.

He turned back to the fifth page of his search engine and clicked on the link for the MLA site, he normally reframed from anything to do with the Meta Liberation Army given their... views on the quirkless, but they had been around longer than All Might and had some pretty powerful quirk favoring ideals so they might have some narrative on 'He who takes' that the mainstream media didn't.

And holy hell did he hit the motherload of knowledge, the MLA had a much different view of 'He who takes' and even gave him a name where most stories didn't brother, "All For One". Apparently, it was in reference to a Pre-Quirk story of the Three Musketeers whose motto was "All for one, and one for all."

The site spoke of 'He who takes' as if he was a real person who was born back during the dawn of the quirk era, and it even went as far as to have accredited him as a founder of the original MLA that had started the Mutant rebellion which kickstarted the first of the three quirk wars, it also leaned heavily into the dealer side of the 'He who takes' stories and regaled Izuku about how he offered people a new chance at life by taking, giving or swapping quirks.

Almost instinctively all of what he had previously been taught made Izuku want to say it was all BS made up by some crackpot in the MLA but the way it was written gave him pause as a lot of the arguments to be made could easily be solved by the man's supposed quirk.

If such an influential man existed why wasn't there any record of him? Well as they say, "History is written by the victor," who would have been He who takes and the only people who would have been around to contest were long past dead as the few immortals that had lived at the beginning of the quirk era were dead from a quirk loophole in their immortality or infants.

Why wouldn't 'He who takes' take credit for all the work he did to free his fellow mutants? (As quirked people were called back then.) Well, that's only assuming the man was wholly a "good" person and history was sadly chock-full of horrid people who took advantage of war and disasters to do awful things.

If such a quirk existed, then it surely would have been recorded somewhere, right? But 'He who takes' could easily pass off someone else's quirk as his own and destroy any records of himself with any number of the quirks that popped up in the three centuries between then and now, leaving nothing but old horror stories passed on as cautionary tales for misbehaving kids.

If such a man did exist surely, he would be dead by now and not be what Zuki was trying to warn him about? Except the man could steal any quirk in existence and Asia has only had one semi-immortality quirk on record in the three hundred years quirks have existed when the international average was three per continent.

Honestly, the more Izuku thought of it the more and more it made sense and horribly realistic it was to him.

Hundreds of thousands of people disappeared or mysteriously died even before quirks existed, who in the world would notice if someone started killing people for their quirks if there wasn't any way to determine if someone still had a quirk after death? Much less check for such a thing?

Why would someone bitter from the world choose to be a part of it anymore when they could live however they want as a myth of man and take any powerful ability in all of existence?

Why would a person treated like a horrid rabid creature by the quirkless majority of three centuries ago not hold an unspeakable grudge against the quirkless?

Feeling like he was losing himself to quickly spiraling thought of terrible things Izuku all but slammed his laptop closed, he found himself trembling as he got up from his bed to check for a fourth time that night that all of the room's locks were shut tight, maybe Izuku was being paranoid after a late-night info binge but as he, and probably many other quirkless people that lived to ten years old had found.

Paranoia could be your worst friend at the best of times and your best ally in the worst times.