Disclaimer: I do not own My Hero Academia/Boku No Hero Academia, or any other property in this work that I did not make myself.

Hizashi Yamada vs. the demon horde

Chapter one: A friend in need is a friend indeed

It was another dark stormy night over at UA High School, Japan's premier hero academy. A number of the men on staff at UA were taking care of some paperwork, mostly in regards to the zombie apocalypse that they had averted a few days prior. However, everyone outside of a small handful of people believes that thirty-eight of the forty students were all killed in an attack carried out by the League of Villains, because the truth not only actually sounds more outlandish, but if believed it'd cause a lot more panic.

Thus, the secret of what truly happened was just that, a secret.

In the faculty office of UA, Hizashi was done grading the last of some assignments from a class he had taught. "There we go," Hizashi said, "That's a perfect score." Curious, both Aizawa and Sekijiro leaned over to see what Hizashi was doing; to their curiosity, Hizashi had graded an assignment that had been done by Izuku Midoriya, one of the thirty-eight students who had been killed in the recent almost zombie apocalypse.

Looking up from the late Izuku's assignment to Hizashi, Aizawa said, "Why... did you grade a paper that Izuku did? I mean he's dead now-"

"Don't remind me!" Toshinori said loudly from where he sat, his tone equal parts sad and annoyed.

Aizawa rolled his eyes. "-So why grade a paper from him?"

Pointing something out on Izuku's assignment, Sekijiro said, "What I want to know is why it's dated from two and a half months ago, well before the near zombie apocalypse."

"Would you guys believe me if I said that I'm lazy as fuck when it comes to grading assignments," Hizashi began sheepishly, "Especially if I let them pile up?"

Giving his co-worker a dry look, Aizawa remarked in an equally dry tone, "That would explain so much, like how Yaoyorozu had always been fretting over her grades in your class."

Folding his arms over his chest, Sekijiro said, "No wonder students from my class and Shouta's would say your class is one of the hardest to pass despite how you're an easy person. You hardly grade papers and assignments, so the credit for those tend to not be counted!"

Sighing in exasperation, Aizawa said, "Hizashi, just focus on grading papers from my class with Kirishima's name on them, and papers from Sekijiro's class with Tetsutetsu's name on them."

"Well that would make being a teacher easier," Hizashi remarked, "Especially considering the fact that I- hey wait a minute, what about Tokoyami's papers?"

"He didn't survive," Hound Dog pointed out as he came over having heard enough, "But his sentient quirk Dark Shadow, who took over Tokoyami's body after you cut the head off, did. And since Dark Shadow isn't a student, you don't have to worry about it."

Hizashi then proceeded to sort through all of the ungraded assignments, looking for ones that bore the names of Kirishima and Tetsutetsu. As he did that, Cementoss came dashing into the room, a mildly wide-eyed look of surprise on his face. "Hizashi!" Cementoss said, catching both Hizashi's attention and the attention of everyone else, "Someone is at the front gate, asking for you! He looks totally soaked from the rain and has a desperate expression on his face!"

"A friend of Hizashi's is here to see him?" Sekijiro said, "And they came in this rain?"

"It's not Luci, is it?" Aizawa asked, his expression and tone conveying suspicion as he folded his arms over his chest.

Shrugging, Hizashi replied, "If it was him, he'd call first to let me know he was coming, then appear near me in either a pillar or upside down pentagram portal of fire." Hizashi got up and went to go see who it was that was asking for him. Aizawa and Sekijiro got up with him, partly because they were worried who this friend of Hizashi's was, given who else the loud pro hero apparently had on his friends list.

...

Holding umbrellas to shield them from the rain, Hizashi, Aizawa, and Sekijiro went to the front gates of UA, went right up to see who it was. At a distance, they saw it was a man; he wore a white fedora, black suit top, white suit pants, and black dress shoes. Hizashi, upon seeing that outfit even from a distance, instantly recognized who it was. Letting out a subdued gasp of shock, Hizashi ran right up to the gate to bring the person inside.

Aizawa and Sekijiro were wondering about Hizashi's behavior here, as they assumed that this friend of Hizashi's would be another person who would take them and everyone else by surprise. Within moments, Hizashi while supporting his friend and trying to cover him with the umbrella that he had, led his friend over to Aizawa and Sekijiro. "Get some hot chocolate made up, stat!" Hizashi said, his tone conveying great worry, "My bud here is cold and soaked!"

"I..." Hizashi's friend said shakily, having a great deal of difficulty in getting the words out, "...I also need a place to hide. I've lost so much of what I once held. I... I am weak now. And I'm being hunted by the last person I'd ever expect to be after my head." Hizashi's friend sounded and looked both desperate and lost, not to mentioned very much humbled.

Aizawa and Sekijiro also took note of the eyes that Hizashi's friend had; sharp and almond-shaped, with plum red pupils that were vertical like a cat's. He also had black hair that was wet and sticking to him, obviously due to the rain. Gesturing to Hizashi's friend, Aizawa asked while partly sounding like he was going to regret asking, "Hizashi, could Sekijiro and I at least get the name of your friend here before we fully take him into UA?"

Smacking himself in the forehead, Hizashi said, "Oh doi, I can't believe that I almost forgot to make the introductions." Gesturing to his mystery friend, Hizashi said, "Boys, this right here is my good pal Muzan Kibutsuji. He's the progenitor of all demons."

...

A short while later in the UA staff lounge, Muzan sat on a sofa while wearing a white men's tank top and a pair of baggy blue swimming trunks, and he wore a towel over his back and shoulders. He was currently drinking from a mug of hot chocolate as Hizashi came into the room, with the eyes of everyone in the room aside from Muzan's turning to look at him; it was everyone in on the secret of how there was almost a zombie apocalypse.

"Okay, I got Muzan's clothes in the dryer," Hizashi said as he dusted his hands, "They'll be good in an hour or so."

"Oh, well that's good," Hound Dog said, a hint of knowing in his tone, "You know what else would be good?" Gesturing to Muzan, Hound Dog snapped at Hizashi, "Explaining to us how you're friends with the progenitor of demons of all people!"

Folding his arms over his chest, Toshinori went on, "Given that he's also somehow friends with the devil himself, we shouldn't be too surprised."

Gesturing to himself, Hizashi began, "I first met Muzan when Luci and I went to a strip club one night a number of years ago on Nemuri's first night working at said strip club because she was strapped for cash at the time and was in desperate need of a side-gig. I went there because I had wanted to be a supportive friend to Nemuri."

"You and Luci met Muzan... at a strip club..." Aizawa said, "...That Nemuri was working at at the time due to needing extra money." Shrugging, the underground hero went on, "What surprises me about that is the fact that the least surprising part so far is that Nemuri had worked at a strip club."

Continuing, Hizashi went on, "Muzan took note of how Luci and I both got the exact same drink, which turned out to be the exact same drink that he got as well. So he joined us, we got to talking about drinks, and within half an hour Muzan was best buds with Luci and I while we were all shit-faced, and Muzan joined me in laughing as Luci got a simultaneous erection and nosebleed due to Nemuri giving him a lap dance."

"Wait, I assume this is before Luci ever learned of Young Midoriya, so I have to ask," Toshinori began, "Who was Luci in the form of at the time?"

"Oh, I had him take the form of Nezu before we went to the strip club," Hizashi explained, "But that's besides the point." Rolling his head a bit, Hizashi went on, "Anyway, Muzan has been joining Luci and I for all sorts of shenanigans ever since we met at that strip club that Nezu has no idea why he's banned from. The guys and I have done everything. Poker nights, monster truck rallies, more strip clubs, you name it!"

Arching a wry eyebrow, Hound Dog said, "The local petting zoo."

Pointing at Hound Dog, Hizashi replied, "Actually yes. And Nezu has no idea why he's banned from the local petting zoo."

"What..." Cementoss began, a bit of apprehension in his tone, "...What did-"

"Luci in the form of Nezu ate one of the bunnies," Hizashi said, "Anyway, back to the main plot at hand." Turning to look at Muzan, Hizashi said, "Muzan, bro, dude. What the hell happened to you?"

Muzan let out a trembling sigh. "...I've lost most of my great, vast powers." Everyone in the room looked a bit surprised to hear something like that, even those who don't know much as they still assumed it to be a big deal. "...I have little else left beyond the standard base array of abilities that comes standard with being a demon," Muzan said, "My only solace is that, surprisingly, I was able to somehow gain sunlight immunity. ...Heh, the one power I wanted to add to my list of what I had, and I got it after losing most everything else."

Toshinori folded his arms over his chest, a look of suspicion on his face. "You're reminding me an awful lot of my sworn nemesis All For One, Muzan Mitsubishi."

"It's Kibutsuji," Muzan corrected, still looking desperate and depressed.

"How did you lose most of your demon powers, Muzan?" Dark Shadow asked, reminding the adults that Dark Shadow, Kirishima, and Tetsutetsu were also there.

Sighing, Muzan said, "A girl who I had wronged ages before the era of those quirk powers you humans love so much. That girl confronted me, fought me. I was so surprised by her challenging me that I didn't even think to try fighting back." Muzan sighed once more. "...And that was a massive mistake, as she was able to use her own demon powers to take most of mine somehow."

"Wait a minute," Kirishima said, "This girl is also a demon?"

"She's used the powers she's stolen from me to infuse her blood into the dead from her time," Muzan said, "Restoring their bodies and raising them from the dead as her own army of demons."

"She raised the dead as demons?" Tetsutetsu said, "This won't be like the zombie apocalypse that we had barely averted a few days ago, will it?"

Holding up his right hand as the left one still held the mug he was drinking from, Muzan explained, "Oh no, they aren't actual undead in any way. They're pure solid demons through and through."

Shrugging, Dark Shadow said, "So what do we have to do?"

Gesturing to himself, Muzan said, "The demon girl who took my place as the lord of all demons is still after me. But for what reason I have no cl-"

*CRASH* *CRASH*

Muzan was cut off when two windows in that room were crashed through from the outside, with two persons landing inside of the room. One was a girl with her dark hair in a bun on the back of her head with a butterfly ornament on it, although the girl also had bangs framing her face. She wore a kimono top with a theme similar to the butterfly ornament, and under that a standard looking dark purple uniform that consisted of a long sleeved top with golden buttons, matching pants, similarly colored tabi socks, and white zori sandals.

The other was a guy, wearing a faded brown version of the uniform the girl wore, and his kimono top, which was worn like a jacket cape, was white with a flame pattern at the bottom. Speaking of flame patterns, the guy wore red kyahan with yellow flame patterns, and even his hair, bright yellow with streaks of red in it, reminded those looking at his hair of fire. Both of these persons had their heads down when they crashed through the windows, and continued to keep their heads down as they stayed still in their kneeling positions.

But then the two of them looked up, showing their eyes were cat-like, and had unusually colored sclera; the girl's was pinkish and matched her kimono and butterfly ornament, and the guy's were red with yellow streaks, also resembling flames.

Gesturing to herself, the girl said, "My name is Shinobu Kocho! My partner here is Kyojuro Rengoku!"

"You humans need not worry about us!" the now identified Rengoku said, "We're only here to take that bastard Muzan with us and present him to our patron lady!"

Pointing at Shinobu and Rengoku, Hizashi said, "Muzan, dude, who the hell are these two jokers?"

Getting up quickly to stand behind Hizashi, Muzan said, "They're Demon Slayers who had died centuries ago, but are among those the demon girl who took my powers had raised as part of her demon horde!" Looking to Hizashi and the others, Muzan said, "You gotta protect me, humans!"

"Given that we want to know exactly what's going on here," Aizawa said as he and most everyone else (Toshinori was leading Kirishima and Tetsutetsu out of the room) stood to confront the demons that broke in to kidnap Muzan, "I guess we have no other choice." The teachers and Dark Shadow all stood ready to protect the progenitor of all demons from two other demons who both wanted to take him and present him to their patron lady.

END, CHAPTER ONE

Author's notes;

This kicks off the second story in the 'Hizashi Yamada vs.' series, and this story also crosses over with Demon Slayer. A mysterious girl demon took most of Muzan's vast powers and is now using them to raise many dead from the final years the Demon Slayer corps was active as demons themselves, and sending them all after Muzan as she wants him for some unknown purpose or another. Hizashi and his co-workers have their work cut out for them, so keep your eyes peeled for more to come.