Disclaimer: I do not own My Hero Academia/Boku No Hero Academia, Overlord, or any other property in this work that I did not make myself.
The Sorcerer Hero: Deku
Chapter one: A new world to conquer?
Ainz Ooal Gown, also known as the Supreme Being who ruled over the Great Tomb of Nazarick, had finally done it. He had conquered all of the New World that he and what all that had remained of his guild from YGGDRASIL had been transported to one day. Now that he was at the top of the New World, he would be able to decide how everything would be ran. But Ainz, known as Lord Ainz to his loyal devoted servants, was not truly heartless despite how he was an undead.
Technically, he never even considered taking over the New World until he learned that his followers were acting on a joking idea Ainz himself said in passing to Demiurge. Under the rule of the undead Sorcerer King, those living in the territories of Nazarick actually knew peace. Ainz had, in the time since he and his guild were transported to the New World, accomplished more in achieving true and lasting peace than what the New World was able to do on its own in centuries.
Yes, all had been settled, and there was nothing left to do. With the New World now his, Ainz had all the time in the world to get used to ruling the world. As such, fate seemed to think that now of all times would be an excellent opportunity to pull Ainz away from it all by having a New World native launch a sneak attack that was able to actually kill the Sorcerer King. Granted, Ainz as he fell over dying saw Demiurge and Albedo kill his assailant, so he knew that he had been avenged.
He also had contingency plans in place to ensure his resurrection, so he'd just pop back in after a time. If anything, this was more annoying to Ainz, although he did learn what the experience of dying was like in the New World so there was that. He spent his last conscious moments before death took him thinking about how he'd reward Demiurge and Albedo for killing his assailant after he was returned to life, as well as how to reward the person who resurrected him.
But the Sorcerer King was surprised when, in a spirit form, he found himself flying through a bright light blue tunnel that was like the water slides of long ago that he learned of in his world before he was transported to the New World. He felt himself dragged through the tunnel of light as he wasn't able to resist the pulling force. He felt as if he was being taken to a second New World, and that this light tunnel wanted to take him there as quickly as possible, as if there was a quest he had to take.
"What is this?" Ainz thought, equal parts panicked by the unfamiliar experience and excited in an interested sense where this could lead. He wasn't sure if he'd be able to return to Nazarick, to the guild he was left behind with. He was deeply, truly sorry to the accomplishments he and his friends had built over the long time YGGDRASIL had been active. Sorry that he was leaving it all behind as this force was taking him to a destination that he couldn't even begin to guess where it was.
...But he was determined to make the most of whatever fate had in store for him next.
Eventually, Ainz's senses returned to him, and looking around he saw that he was in an alleyway in Japan. ...Wait, Japan? Was he somehow back in the hellish world that Earth had become in his time? ...No, wait, this Japan looked nowhere near as polluted, nowhere near as taken over by greedy corporate weasels. It looked like the kind of Japan that existed well over a century before Ainz in his original life had been born.
It was still technologically developed, just not to the level he remembered seeing before he was transported to the New World. Well, Ainz had no idea how developed this version of Japan was as he was in an alleyway. He also noticed that he was still in spirit form; it would appear that he didn't gain a new corporeal form upon being transported to this second New World, this second Japan. He did, however, feel that he still had all of his spells and powers; he could even tell his level was still sitting at one-hundred.
He also noticed some new powers, and he still felt he had access to what all items he had on hand at the time that assailant got him. But he couldn't activate any spells or powers, couldn't access any items, while he was in spirit form. Try as he might, the Sorcerer King was, for lack of a better term, weak and powerless in this spirit form. "It would appear that I need to find a way to gain a corporeal form in this second New World in order to do anything here," Ainz thought.
The spirit Sorcerer King figured that he might have to figure out a way to communicate with one of the people living in this second Japan, to help him find a way to get a corporeal form. He'd prefer a human form, maybe he could either possess a human or influence one to kill another human then Ainz could take over the then dead human body. Or perhaps he could find a morgue and pick from the cadavers there. Ainz, having long since grown accustomed to his undead mindset, wasn't picky.
It was as the spirit Sorcerer King flew around the alleyway, wondering if he could be seen as well as where the exit was, that he came across a peculiar sight; a boy wearing a Japanese junior high school outfit was laying face on the ground in the alleyway. The pool of blood told Ainz that the boy was dead. Ainz looked at the body, then looked up at the top of the buildings surrounding the area they were in; Ainz reasoned that the boy committed suicide by jumping off of a rooftop.
Ainz turned from looking up at the top of the buildings surrounding the alleyway to back down to looking at the dead boy. Fair skinned, and with a medium long length of green messy hair. He also had freckles on his face and his eyes, the light of life having fled from them, were also green. Even though he was an undead and in a spirit form, Ainz felt his heart ache for this dead boy. Regardless of his feelings for the dead boy right now, Ainz would still be able to make use of his help.
"This poor young man must have faced insurmountable odds in his life if he decided to take his life and in such a fashion," Ainz thought as he tried to possess the dead boy's body, finding that doing so was as easy as pressing his spirit form into the dead body, "But I am grateful to him, I will do what I can to thank him for his sacrifice." After Ainz entered the dead boy's body, he felt some manner of force seal him into it; he was able to get in, but he could tell he'd be unable to get out. No turning back now.
Ainz felt what all damage the dead boy's body had heal and mend as his spirit got used to the new vessel. He also felt a flood of memories hit him, memories that he knew full well weren't his. It was then that Ainz realized that he had inherited the memories of the dead boy whose body was left for Ainz to take for his new corporeal form. Ainz was first able to learn the name of the boy whose body was now Ainz's; the boy's name was Izuku Midoriya.
Thanks to Izuku's memories, Ainz got a pretty good picture of how this second New World worked; it was like the world he lived in before being transported to the New World with his YGGDRASIL guild, but set well over a century prior to the time Ainz was transported to the New World. In this second New World, eighty percent of the world's population had amazing powers called quirks, and the society of this second New World basically revolved around them.
Izuku, in life, was one of the very rare and very unlucky persons to not have a quirk, having been diagnosed as quirkless. Whether or not someone would have a quirk was determined the moment someone was born, but quirks typically don't manifest immediately. Back when Izuku's quirkless diagnosis came out, he was shunned by everyone because of it, viewed as being less than human due to sheer accident of birth. But Izuku didn't give up. ...Right away, that is.
Despite his quirkless diagnosis, Izuku had dreamed of becoming something called a pro hero, persons legally licenced to use their quirks to fight crime and help keep society clean. It reminded Ainz of some old comics he read a long time ago. But circumstances kept pushing Izuku down, and the straw that broke the camels back was when All Might, who is ranked as this second Japan's number one hero, told Izuku he couldn't be a pro hero without a quirk.
Izuku, after All Might leapt away from the rooftop he left the boy on, then walked to the edge of the roof overlooking the alleyway and jumped, with the rest being history. From what Ainz figured, Izuku had committed suicide roughly five minutes prior to Ainz's arrival in this second New World. After Ainz got used to the flood of Izuku's memories, he stood himself up, dusted himself off a bit. He noticed Izuku's items laying on the ground near an open backpack that was also Izuku's, so he went and gathered all of it.
Standing up alone in the alleyway, Ainz tried to access his powers, spells, and items again. To his delighted surprise, he was able to do so. He was even still level one-hundred, and still had all seven-hundred plus spells he got. However, he noticed he had a new trait next to his Dark Wisdom which granted him the ability he had to learn his totally absurd number of spells. Checking it out, Ainz saw that it was called Expanded Vessel.
It raised his spell limit to an even eight-hundred, and he saw that some new spells were already added; Portal to Nazarick, Detect Quirk, Harvest Quirk, and Bestow Quirk. The Portal to Nazarick spell had caught Ainz's attention immediately, and reading it he saw that it would conjure a portal that would allow him to go back to Nazarick. If he cast it inside of Nazarick, the portal that would be conjured would bring him back to this second Japan.
"Oh, Izuku Midoriya," Ainz said to himself as his undead heart filled with sincere appreciation, "You truly are far more valuable than the people of this world gave you credit for." He held out a hand, felt his magic flow through him. "Portal to Nazarick." A swirling portal, not unlike what is made with the Gate spell, appeared. Eager to return, Ainz stepped through the portal, hoping that things wouldn't be too hectic upon his return.
...
In Ainz's office back in Nazarick, Albedo and Demiurge were struggling to carry out work to set up the resurrection of their master so that he could take his rightful place as ruler of the New World, a right he had just earned earlier that day. Albedo was also practically in tears, as Ainz was the love of her life and he had been vanquished. It was as the two most brilliant of Ainz's loyal devoted NPCs were rushing about their business that a portal appeared in the office to the left of Ainz's large and grand desk (if one stands in front of it).
"Who goes there?!" Demiurge demanded angrily, already on edge as the only Supreme Being who stayed behind was in need of resurrection, "You had picked a bad time to-"
"-Come back and apologize for my faux pas of dying and leaving you alone for a moment?" a voice called out, cutting Demiurge off. The voice was unfamiliar to Demiurge and Albedo, but at the same time it was very much reminiscent of their beloved Lord Ainz. Stepping through the portal was a green haired human boy who looked pale as the dead, and was wearing what Demiurge was going to assume was some manner of academy uniform.
Holding his right hand out to Demiurge and Albedo, the boy said, "It would seem that not even death can stop me, Demiurge and Albedo. Fate had brought me to a second New World, granted me this new form with all of my powers, spells, items, and level as well as some new abilities." The boy then exuded a deathly aura, it washed over Demiurge and Albedo, albeit gently enough to not cause any harm to either of them.
But that aura... only one person they knew of had such an aura! Albedo, tears in her eyes, rushed to the boy. "Lord Ainz!" Albedo said, the tears of joy running down the sides of her impossibly lovely and beautiful face, "It truly is you! You came back to us!" Albedo threw her arms around Ainz's neck and pulled him into a hug that shoved his new face right into Albedo's ample breasts. Albedo then cried in relief as Ainz was back, and even Demiurge cried in relief.
Ainz figured that Izuku Midoriya would be very much flustered by it if he were hugged by Albedo the way she was hugging him right now.
When news of Ainz's surprise resurrection and return reached the people of the Great Tomb, all came to see their returned master. Granted, they were surprised by his new form even if it was still undead, but they could sense his specific power, his presence. Ainz had returned, and as he sat in his throne in the throne room, dressed in his usual outfit once more, he held a hand out to all who were gathered before him.
"My loyal followers," Ainz said, "I would first like to express my thanks to a boy by the name of Izuku Midoriya, for it was his sacrifice that permitted my gaining of a corporeal form in the second New World that I was transported to upon my... less than pleasant encounter earlier this day."
"Is that the name of the boy whose body is now your new body, Lord Ainz?" asked Shalltear as she raised her head while still kneeling before her lord.
"Indeed, Shalltear," Ainz said; he had an illusion spell he could have used to appear as his original skeletal self, but he went without it, showing his loyal followers what Izuku looks like so that they all knew the appearance of the boy that they owe thanks to for helping Ainz ultimately return to the Great Tomb.
"Lord Ainz," began Cocytus, "What is this about a second New World that you speak of?"
"I'm glad you asked, Cocytus," Ainz replied, "In the process that led to my resurrection, I had been transported to a second New World, but I had gained the means of returning to this one. We have already taken over all that this first New World has, so I was thinking of taking over the second New World that I had been transported to. I can go back and forth between this world and the second one at will."
Aura, looking concerned, raised a timid hand before she said, "You... you aren't going to leave us like the other Supreme Beings did, are you?"
Ainz laughed in understanding amusement. "My apologies, Aura, I did not mean to cause you or anyone else here undue concern with my plans of taking over the second New World," Ainz said, "And to answer your question, no I have no intention of leaving all that my fellow Supreme Beings and I had created together behind. In fact, my new ability to move between this New World and the second New World may let me bring folks from both New Worlds to each other."
The residents of Nazarick lit up with excitement. "Does that mean we can accompany you on your inter-world conquests, Lord Ainz?" Shalltear asked.
"I still have to see if I can bring people from one New World to the other New World and vice versa first," Ainz replied, "But if I can, then I intend to make full use of all that is here in the first New World we had conquered and use it to aid in my plans to conquer the second New World!" All of Ainz's loyal devoted servants cheered at their master's plans. As the demons, undead, and other monsters all cheered, Ainz had a serious thought go through his mind.
"I owe everything since my recent death and resurrection to Izuku Midoriya. I will do all that I can to grant him the wish he had to become a pro hero in his world. I will also aim to make his world a much better place. And who knows? Maybe I'll have a little fun along the way, especially as I test out my new spells and abilities. Oh, Izuku Midoriya." The crowds before Ainz cheered as he sat in his throne and pondered how to go about conquering the second New World.
"You're a hero to me."
Later in the evening in the second New World, Ainz stepped through a portal into the alleyway where Izuku had died earlier that day. Ainz was back to wearing the outfit Izuku was wearing at the time of his death, having been cleaned by magic to remove the dirt and blood. Thanks to the memories he had inherited from Izuku, Ainz knew where the boy (prior to his suicide) had lived; in an apartment complex with his mother Inko.
Ainz, shifting through Izuku's memories of where he lived, learned of a secluded area in an alleyway behind the apartment complex where there'd be little chance if any to be seen. Ainz could cast Gate to conjure a portal and simply walk there in a matter of seconds, or perhaps he could just cast Time Stop to freeze time and walk to the apartment complex at his leisure. The Sorcerer King decided on just casting Gate, it'd take a bit less mana despite how his mana exceeds all limits and casting even Time Stop wouldn't put much of a scratch into it.
Right as Ainz was about to cast Gate, he heard a voice call out, "Oi, kid! Bad time to be lost and alone, wouldn't you say? Heh heh heh..." Ainz turned to see a street thug looking fellow approach him, a spiraling copper-looking spike about fifteen centimeters coming out from the palm of his right hand but clearly causing the man no harm. Ainz arched a wry eyebrow at the man who he was figuring was intending to try to mug him.
Gesturing to the man, Ainz said, "And you are...?"
"The man telling you to take out all of your valuables, drop them, and leave unless you wanna die," the man threatened.
To the man's (mildly unsettled) surprise, the boy in front of him laughed in his face. "You really think that you are a threat to me?" Ainz asked, "I have faced greater horrors over lesser deals and those still couldn't make me blink!" The man, pissed now, tried lunging for the boy in front of him, having not even the slightest clue that the boy in front of him was Ainz Ooal Gown.
The man was barely able to get two centimeters forward before Ainz cast Time Stop, freezing time all around... well, Ainz had no idea of the range, but he felt it comparable to the time he used Time Stop to freeze everything in place when he had his duel with Gazef. That said, it wouldn't surprise Ainz if time was stopped for all of this second Japan, if not the whole of this second New World. The Sorcerer King then walked up to the frozen in time thug.
"Now would be a good chance to test out my other new spells," Ainz remarked to himself. He first held his right hand to the thug and said, "Detect Quirk." After a briefly glowing magic circle appeared, Ainz saw an info screen appear in front of the thug. It gave the thug's name as Kakuzu Shimura, and his level as eleven. Ainz then took note of two numbers under Kakuzu's name and level; one number was labeled as Quirks and was at one, and the other number was labeled as Quirk Capacity and was at two.
Under that, the Sorcerer King saw a message that said 'Kakuzu Shimura has the following quirks;' and under that Ainz saw an info box like one describing an item in one's inventory. There was a picture of a spike like the ones coming out of Kakuzu's palms in the quirk description box next to the following information;
Copper Palm Spikes (Transformation-type quirk)
This quirk allows the user to grow copper spikes from the palms of their hands. These spikes when grown are fifteen centimeters in length. To use these spikes for combat, the user has to make palm strikes on the target as the spikes can't bend and be held like knives.
Ainz closed that menu, then aimed his right hand at Kakuzu again. "Harvest Quirk," Ainz said as another small glowing circle of magic appeared briefly. To Ainz's surprise, a small dark swirling portal appeared on Kakuzu's person, and a light purple crystal like gem the size and shape of a baseball came out before disappearing. Ainz then saw a small message to his lower left that said 'Quirk Jewel: Copper Palm Spikes has been added to your inventory'.
"Quirk Jewel?" Ainz said, equal parts surprised and curious. Wanting to test things out more, Ainz cast Detect Quirk on Kakuzu again and got the same menu as before, but with the difference of there being a message that said 'Kakuzu Shimura is quirkless.' in place of where the info box that detailed Copper Palm Spikes used to be.
Closing that menu, Ainz decided to test his third new spell. "Bestow Quirk." As the small circle of magic glowed in front of Ainz's out held hand, he saw a menu pop up that said 'Please select a Quirk Jewel to use.' and beneath the message was a list he could scroll down for options, but the only option he saw was Quirk Jewel: Copper Palm Spikes.
He selected that, and then Ainz saw the gem he saw earlier merge into Kakuzu's form as the message 'Quirk Jewel: Copper Palm Spikes has been removed from your inventory' appear in the lower left of his vision. Casting Detect Quirk again, Ainz saw the same menu that he saw the first time before he tested out his Harvest Quirk spell.
"Ah, I see," Ainz said, "The new spells that I had gained, in addition to allowing me to move back and forth between Nazarick and this second New World at will, are equipping me to better work in this second New World that clamor around its quirks. I ought to write down everything that I learn as I go about my business here."
Ainz then cast Harvest Quirk on Kakuzu again, getting the Quirk Jewel containing Copper Palm Spikes back. After the jewel was added to his inventory, Ainz read the description of the Harvest Quirk spell. It took a quirk from the target, leaving them without that quirk, and the taken quirk is put into a jewel that's created and then added to the caster's inventory. Ainz also saw that Harvest Quirk's description said 'Quirks taken with this spell will not have vestiges (imprints of the quirk's original owner) attached to them'.
"I will have to make a note of that," Ainz said, "There is so much in this second New World that I am ignorant about, and being ignorant simply will not do." Ainz then looked to Kakuzu, who had been stuck in place as Ainz still had Time Stop active. Ainz held a hand in front of Kakuzu's face, a lot closer than he did with his new spells, before he cast a spell he already had.
"Delay Magic. True Death."
A dark aura glowed around Kakuzu's frozen in time form before fading. Ainz then walked to the entrance of the alleyway which he had been able to spot. The moment that Ainz stepped foot out of the alleyway, he ended Time Stop, allowing things to resume as normal all around. Kakuzu fell over dead in the alleyway behind the Sorcerer King, making at most a thumping noise that many could mistake for a bag of trash being tossed into the alleyway.
"Well now," Ainz said to himself, running on the memories he had inherited from Izuku, "Time to go on home. I'll have to find another secluded place to hide and cast Gate. I hope Izuku's mother won't be too upset with my late arrival."
Ainz was able to get to the apartment complex where the Midoriya family lived easily enough. Ainz found the apartment that Izuku lived in prior to his suicide, opened the door and walked in. Ainz was greeted by the sight of Izuku's mom Inko; a woman who looked to be somewhat shorter than her son, and looked like an adult woman version of Izuku save for longer and straighter hair, also Inko was a bit on the plump side.
Inko, tears in her eyes, ran to Ainz and threw her arms around him, not knowing it was Ainz who was now inhabiting the body of her son. Apparently, she thought something bad happened to Izuku, given how long he'd been gone even with his school day that day taken into account. Inko also took note of how Izuku looked 'as pale as death' and he was a bit cold to the touch.
"I had a rather frightening encounter earlier with some nasty fellow who grew spikes from the palms of his hands," Ainz said, "Luckily for me, a hero came by and defeated the fellow, saving me from trouble. The hero had me stay for a bit as he needed info from me, then allowed me to go. I still had to let my nerves settle afterwards, the encounter with the thug was that disturbing. I apologize for any undue distress I had caused you."
Ainz's story was one that Inko bought hook, line, and sinker. "Well thank goodness nothing serious happened to you, Izuku," Inko said, "Oh, there's leftover dinner in the fridge if you're hungry."
"I appreciate it mom," Ainz said, "But for now I think I'd like to go to my room and rest." Inko nodded in understanding, allowing (who she thought was still) her son to go to his room. There, Ainz would have the privacy he'd need to do some work.
...
Ainz saw that he also inherited Izuku's academic prowess and knowledge, and using it was able to do what all homework Izuku had; the Sorcerer King wasn't going to let his new vessel fall behind in school, especially since Izuku was able to get more schooling than what Ainz himself got in his time before he and his guild were transported to the first New World.
After taking care of all of that, Ainz got to work on writing out a book about what all he's learned about this second New World since he got here. He also wrote about his new quirk related spells and what all he observed from them. He made a note about wanting to learn more about the Quirk and Quirk Capacity numbers that are shown on the Detect Quirk menu.
After he finished writing all of that out, Ainz reached into his inventory, making a swirling black portal appear, grabbed something, and pulled it out. It was the Quirk Jewel he got from Kakuzu after the second use of Harvest Quirk. Examining it, Ainz saw a simple description that said 'A Quirk Jewel containing the Copper Palm Spikes quirk.' over the jewel. He exited the small description menu and simply held the Quirk Jewel.
Looking at the Quirk Jewel, Ainz remarked, "Marvelous. There truly is quite a lot that I need to learn if I am to make any progress in my work here." Ainz then placed the Quirk Jewel back into his inventory. Looking at the time, Ainz saw that it was close to four in the morning, and yet he felt not the slightest bit of exhaustion. But then again, Ainz IS an undead, and as such has no need for sleep, or various other things for that matter.
Having no need for sleep will increase how much time Ainz will have on his hands, which is a good thing as he'll be needing all the time he could get to focus on what all work he needs to do as he plots how to take over this second New World, while making Izuku Midoriya a top name in the field of pro heroes.
END, CHAPTER ONE
Author's notes;
This is the first chapter of a BNHA/Overlord crossover idea I randomly came up with. Here, Ainz after successfully conquering the New World is vanquished, but his spirit goes to the BNHA world. There, Ainz takes over the body of Izuku who took Bakugo's advice after All Might crushed the last bit of hope he had.
Ainz gains a number of new spells, one letting him return to Nazarick to the great relief of his followers, as well as giving him the idea of taking over multiple New Worlds as he plots to try and do in Izuku's world what he did in the New World, while at the same time granting the late Izuku his wish to become a pro hero.
Ainz tests out his other new spells, and from that learns a few things he'll be making use of later on down the line. Ainz then goes to the Midoriya apartment and takes care of a few things before he writes down his observations he's learned since coming to Izuku's world. Things will continue from here in the next chapter.