(Not) Used to the Darkness

(Inspired by Destiny)

Izuku is a Guardian, a defender of the Light, the Traveller, and the Last City. He has fought against the Eliksni House of Wolves, the Taken and the Hive, and the Red Legion…

And then, one day, during a battle with the Vex, he and his Ghost, Mikumo, wakes up in another world. Another Earth. An Earth filled with people with powers, with quirks.

Izuku and his Ghost spend some time wandering around Japan, rolling as a vigilante for some time as they worked to help as many people as they could. However, their violent methods of taking down villains, of which would've been normal or even restrained within the old world that they had come from, would leave them alienated by the public and branded as villains themselves by the heroes.

Soon enough, it is All Might that catches Izuku and his Ghost during their raid on the hideout of a pair of villains known as Martial Hair and Needle Hair, and the Guardian and his Ghost are forced to surrender to the heroes in order to save themselves.

Upon learning of Izuku and his Ghost's intentions, and also after forcing them to tell him about their past, Nezu decides to shield the two of them from the HPSC and shelter them within U.A., seeing the potential in them to become heroes. Izuku goes through the recommendation exams with the likes of Setsuna, Yaoyorozu, Todoroki, and the others, and passes, and is soon admitted into Class 1-A. Along the way, Mikumo, his Ghost, regularly makes comments on the amount of Light that he can feel from everyone around him.

Soon enough, the beginning of the school year begins, but Izuku is unable to rank high in the scoreboard of the quirk application test due to his powers in the Light, his being a Titan, not having many appliable uses in such a test, leaving him in the bottom half of the ranking structure. However, during the next day's battle trials, Izuku is able to dominate his opponents thanks to both his combat orientated Light powers and his wealth of experience, and this nets him several rivals within Class 1-A, particularly Todoroki, Bakugou, and Momo, who is shown to be much stronger in this fic than she is in canon, and ends up becoming the MP of their round due to Izuku's violent usage of his Light and his lack of care toward the destruction of property around him.

A few days later, Izuku ends up voting Momo as the Class Representative over himself, with her becoming class representative and Iida becoming vice representative. During the break-in later that day, the three of them are able to work together to calm down the students, and cement their friendship with each other later that day.

(The key that I've got for this story is to keep Izuku as powerful as a guardian should be, but also with some logical weaknesses to keep him grounded, as well as some flaws to keep him human.)

During the USJ Incident later in the week, Izuku would come face to face with many of the villains that had joined the League of Villains in invading U.A., and he would realise that many of these villains had been ones that he'd fought and beaten before, a few even brutalised in fact, with many of them, particularly Martial Hair and Needle Hair, had joined the League in hopes of getting their own back on the former vigilante. Izuku would go on to defeat them, but would be forced to consider his methods on how he defeats his enemies in this new world, especially if he wants to stay in line with the laws that govern this world as world. Worse yet, his brutal methods against the USJ villains would only serve to frighten many of his classmates, alienating him from the rest of 1-A save for his closest friends.

When the Sports Festival came to pass, Izuku would blitz through the course, as it was now suited to his particular skillset of Light powers. First, he used his Sparrow and double jumping to best the first event, but is barely able to scrape past the second round with his team composed of Momo, Mei, and Shoji, thanks to the likes of Bakugou, Todoroki, and other teams targeting them. When the third event came to pass, Izuku would almost be stopped by Shinso during their match.

However, when Shinso is able to use his quirk on Izuku, instead of doing as Shinso commanded in walking off the stage, Izuku goes catatonic as his mind drifts away into the Light. In this state, Izuku's mind goes into a form of death, and he begins to hear whispers from a dark force that rested itself within their world. A voice using the powers of the Darkness itself.

Izuku's Ghost would be able to snap him out of his stupor, but Izuku would be unable to continue the Sports Festival as he is rendered into shock at his experience with the Darkness, something that he thought he had escaped from. As it is now revealed, Izuku has a deep seeded hatred and fear of the Darkness, so much so that when other Guardians had started using Stasis back in his homeland, Izuku had been disgusted by it to the point of openly challenging them in the Crucible over it. To him, the Darkness was something to be fought and confronted, not bartered with and used for power. As such, he had never got along with the likes of the Drifter and Eris Morn.

Meanwhile, Bakugou and Todoroki would continue the Sports Festival, unsatisfied as they had both wanted to challenge and battle Izuku on the field. However, they would both be defeated by Momo, who would go on to win the Sports Festival and earn All Might's attention, all the while many in the public would begin to make the connection between Izuku and the violent vigilante that had been running around before the start of the school year, and would scorn him for it.

Soon enough, Izuku would go out on his first internship, but would find himself straddled with Eraserhead due to his lack of offers for internships. The two of them would constantly butt heads over what is the best thing to do in a situation, with Izuku wanting to go out and save as many people as possible and Eraserhead restraining him from doing so. Eventually, the two of them would head into Hosu during the League of Villains' attack on the city, and Izuku would break away from Eraserhead to go confront Stain, who was just about to kill Iida and his mentor. However, during the battle, Izuku would find himself on the backfoot against Stain, who was somehow even more powerful than he could've imagined. It took the combined power of Izuku, Todoroki, Eraserhead, Endeavour, and Gran Torino (who had been training Momo for All Might), to take him down, and even then it was a difficult duel.

And then, Izuku would see the object that Stain had been carrying that gave him all his power, and he freezes up.

It's a splinter shaped like a pyramid. A Splinter of Darkness.

Eraserhead is forced to restrained the enraged Izuku before he can kill Stain, and later on, gives the boy a major dressing-down, telling him that he would've expelled him and sent him off to juvie for that if it wasn't for Nezu protecting him. Meanwhile, Nezu asks him as to why he had reacted so violently to the object that Stain had in his possession, but Izuku would refuse to answer, simply saying that it was too dangerous, and needed to be destroyed.

Meanwhile, the Splinter is taken away as evidence, only to corrupt the mind of a police officer who takes it for himself, only for himself to be killed by a gang member and stolen away. A few days later, a gang war would start over it, as the stray Splinter would begin to drive others into a greedy sense of madness, before eventually falling into the hands of one Shoto Todoroki, as it begins to whisper to him and feed his anger at his father.

Soon, the final exams would begin, and Izuku would find himself side-lined and denied entry into taking the exam as punishment for his earlier actions, with some in the staff considering revoking his chance at getting a licence due to his actions as a vigilante earlier. However, Izuku would begin an investigation of his own into the Splinter that Stain had on his possession, and how it linked to the voices that he'd heard when he was under Shinso's control.

All Might, seeking answers of his own about Izuku and hoping to find some time to spend with his chosen successor, would take both Izuku and Momo up to I-Island, allowing him to see his niece Melissa, who reminds Izuku too much of someone from his past, meaning that he finds himself unable to stay in her presence for too long.

Meanwhile, Todoroki arrives on I-Island, following the whispers of the Splinter in his possession to go down into the depths of the artificial island to find what he needed to help him get his revenge on Endeavour.

Meanwhile, Izuku and Momo would find themselves alone, and the latter would begin to prob the former over his reactions to these things of darkness, as he called them. Momo would guess that his reactions were because he had lost someone like Melissa a long time ago, but kept that to herself, and continued to prod Izuku for information and reactions. Izuku, however, would begin to poke at Momo with questions of his own, as he realises that Momo knows way more than she's letting on.

However, they would soon be interrupted by an alarm. I-Island is under attack… by Todoroki, who has been corrupted by the Splinter of Darkness in his possession and is tunnelling down to the bottom of the artificial island.

Izuku and Momo go to intercept, with Momo continuously restraining Izuku from going at Todoroki and killing him for possessing the Darkness, telling him that the dual-quirk user is as much a victim as everyone else. Izuku refuses to hear it, but forces himself to concede the point, remembering what he has been told by Nezu and Eraserhead before.

Soon enough, the two of them chase down Todoroki through the bowels of I-Island, and Izuku is shocked to find that the scientists of the floating island had been studying other artifacts of Darkness, sickening him, though he is left confused as to why they were here.

He would soon find his answer when Momo and he reached the lower depths of the island, and Izuku is shocked at what he finds.

A Pyramid. An obsidian Pyramid belonging to the Black Fleet.

Izuku and Momo follow Todoroki inside, and they find him kneeling before a statue of a veiled woman, having stabbed himself with the Splinter and let it worm itself into her body and fuse its power with himself.

Around them, a legion of Taken, now under Todoroki's command, as well as a new Darkness enemy that Izuku doesn't recognise known as Tormentors, spawn into existence, and begin to attack them, whilst others move to invade and take over the rest of I-Island. Izuku flies into a blind rage at Todoroki's usage of the Darkness, but is unable to stop him from escaping with his pair of Tormentors as more Taken move to block them.

Soon enough, they break out of the Pyramid and move to assist All Might and the rest of the heroes in kicking the Taken off the island, but find themselves being overrun by their enemies, with David Shield and his cadre of scientists revealing that they have been corrupted by the Pyramid's resonant energies as well and open the floodgates for the Taken to move through.

However, right as they are on the verge of defeat, Momo reveals her true colours as she makes a move of her own to take the island, and unleashes her true power.

She is a Guardian herself.

And her Ghost belongs to the Lucent Hive.

Momo is a Lightbearer in league with the Lucent Brood, and at her call, swarms of Lucent Hive invade I-Island and take over, beating back the Taken into the Pyramid and wiping them out, and Izuku, All Might, and the heroes are forced to retreat as they are overwhelmed by the Hive, who begin to push their home, the throne world, into real space and terraform the entirety of the artificial island to their suiting.

And Izuku, upon learning of this, is forced to fight against Momo and her subordinates, meaning that he is forced to run from her Hive Lightbearers, shattering her belief in the Light and destroying everything that he has ever believed in. This is only made worse when he encounters Melissa, who herself has been in league with Momo and the Lucent Hive as well in challenging the Pyramid and the Darkness, and he is rendered catatonic and has to be dragged away by All Might in a hasty retreat.

Izuku, in all his career as a Guardian, has never thought the Lucent Hive before, so this is all a fresh experience to him, and completely eviscerates everything that he has ever believed in.

And here is where we finally get into Izuku's backstory, where we see that, a long time ago, he had a wife, a fellow Lightbearer, and they had a pair of adopted children together. Back then, he had been more willing to entertain using the Darkness to defeat their enemies, and had even been a close reader of Ulan-Tan's thesis about his theory of Symmetry between the Light and Darkness.

However, during the events of Season of Arrivals, Izuku would find that his wife had succumbed to the corruption of the Darkness by the arrival of the Pyramids, and had murdered not just her Ghost, but their children as well, before killing herself right in front of Izuku and laughing all the way.

Ever since then, Izuku had turned away any sense of learning or using the Darkness, and had become violently dedicated to upholding the Light and opposing the Darkness. This led to several problems where he got into confrontations with Guardians who had begun to use Stasis, particularly the Young Wolf, and would decide to leave the Last City behind when the Vanguard made an alliance with Caiatl's Cabal Imperium and allowed the House of Light to shelter inside the city.

But now, with the Darkness well-intrenched inside Earth, and the Lucent Hive, an enemy that he has never faced before, who can also use the Light, something that he thought was sacred and untouchable, Izuku finds his entire worldview shattered and left in pieces, leaving him lost on where to go and what to do in a world that hates him.

And with the Taken now on the field, Todoroki and other heroes being corrupted by the Darkness and using the Taken to further their own purposes, and Momo leading the Lucent Hive into gaining a foothold on Earth to oppose not just the Darkness and the Taken, but also Hero Society as well, Izuku must soon take to the field once more and move beyond his narrowminded worldviews, accepting that to fight and win this war, he must use every advantage that he can get to survive the coming struggle.

Especially when the powers of Stasis and Strand call to him so…