A/N: So apparently I can only write things without doubting myself and deleting pages of work until I eventually leave everything unfinished when I'm drunk. Maybe I'll proofread this when I'm sober, maybe I won't, who knows. This was pretty much completely inspired by the line "Meddling when you don't need to is the essence of being a hero." It has little context, not much extra thought put in, and I don't particularly care to explain why good old Deku is wandering around in the world of Miraculous Ladybug. If anyone wants to take this and make it into an actual thing, go right ahead, because I probably won't. I've tried to write entire fanfictions before, and they never got completed at all. So, enjoy what nonsense I can produce.
The first time Midoriya Izuku saw an Akumatized villain, he was far too shocked to react immediately. The sight of a man in a pigeon costume riding on a cloud of the animals that he seemed to want to mimic was jarring enough to throw even him off his game for a minute. After a good mental shake, he had begun his customary analysis of this person's powers, putting his shock over the first quirk-like thing he had seen in years behind him for the moment. After a few moments of processing, customary muttering of observations drawing him the same odd looks as always, he suddenly realized that he didn't have any sort of Hero outfit with him, and cursed under his breath, as he didn't think showing his powers in his true persona would be wise until he knew a bit more about what in the world was going on.
A bit of research after the odd, but aptly named "Mr. Pigeon" had been defeated led Izuku into learning about the strange villains that plagued Paris, and the heroes Ladybug and Chat Noir that defended the city whenever villains such as Mr. Pigeon appeared.
Of course, there were some questions that weren't answered just with public knowledge and the information contained by the very helpful "Ladyblog." Why did this "Hawk Moth" want the items possessed by Ladybug and Chat Noir in the first place? If that was the only reason these attacks were happening, why didn't Ladybug and Chat Noir try to negotiate a deal with him? Normally Izuku wouldn't even consider striking a deal with a villain, but in this case, if all the villain really wanted was to get his hands on these artifacts, then it almost seemed like giving him some of what he wanted would save a lot of effort, and potentially lives in the long run. However, Izuku also trusted that his fellow heroes had good reasons for not giving in. Most likely, the true villain behind these attacks had a much more nefarious goal behind what he was doing.
The second time Izuku saw an Akuma in action, he didn't really have time to do anything to help. After his first sighting and his research into the villains that occasionally popped up, he had made a suitable approximation of his hero uniform that he tried to keep on hand whenever he could, but in this case, by the time he had caught sight of the strange, mime-like villain, he was already being defeated by the local heroes, so Izuku saw no point in attempting to intervene, especially when it would reveal his presence to the enemy for no good reason.
Frankly, the number of close calls that Ladybug and Chat Noir had apparently had in their previous fights alarmed Izuku. It was one thing for a truly fearsome villain like Stain or Shigaraki Tomura to put a hero on the ropes for a while, but the villains that Chat Noir and Ladybug tended to face didn't seem to be anywhere near the same league from Izuku's view. And yet there were a few incidents where the local heroes had been just a hairsbreadth away from losing everything. There were no Pro Heroes or heroic academies in this world that Izuku had somehow found himself in, but Ladybug and Chat Noir seemed to make a lot of mistakes even for people without formal hero training. Sure, there were plenty of villains that they put down with no problem whatsoever, leaving Izuku to only hear about these villains hours or even days after they had appeared, but there were enough cases where the villains had almost won to make Izuku nervous. So, he eventually decided that it would be best to keep his power and willingness to help as a secret trump card for the moment. While he wouldn't hesitate to step in to save a civilian or turn the tide of a battle that was looking bad, revealing himself over a villain that was already defeated would be pointless.
In any case, he usually didn't have to even make that decision to begin with, as he was often too far away to do anything about the Akuma before they were defeated by Ladybug and Chat Noir. He was thankful for this, since this trend proved that despite the close calls he had heard about, Ladybug and Chat Noir weren't incompetent as heroes.
There were several other Akuma that Izuku heard about just in time to be worried, but not in time to help out, which frustrated him to no end. He was quick to remember his first lesson with All Might, and how the #1 Hero had remarked that the most dangerous villain activity actually happened indoors, out of sight from the public. He couldn't help but acknowledge the truth of this statement, even if the actual results of it were so infuriating to him.
However, there was one weakness to the akumatized villains, and one that he had taken note of quite early on; Hawk Moth had to send a corrupted butterfly to his victims before they could become supervillains themselves. This meant that for a short while, the future villains would be vulnerable, or, rather, the butterflies that would corrupt them would be vulnerable. Izuku hadn't yet had the chance to begin locating Hawk Moth's lair based on the flight patterns of the butterflies, but he fully intended to take advantage of this single weakness any way he could.
Seeing a black, glowing butterfly fly through the streets of Paris as he was walking through the city was more than enough for him.
He had to duck into a secluded alleyway and rush through a change in costume, but it took him very little time to transform himself from the unremarkable Midoriya Izuku into the green-clad Deku, hero-in-training and heir to the power of All Might. Unfortunately, even he couldn't change fast enough to keep continuous sight of the insidious Akuma, so he simply made his way to the rooftops and began making his way in the direction he had last seen the butterfly moving, keeping an eye out for anything amiss that would signal the presence of the villain that was sure to appear.
Izuku didn't have to wait long before he saw signs of a battle being fought. A car split in two and the red blur that was Ladybug leaping into action were plenty obvious even from far away. It wasn't long after that before he saw a situation that made his blood run cold. Ladybug stood on a rooftop, interposed between the obviously Akumatized villain and a civilian in a fencing uniform. Izuku's keen sight easily picked up on the fact that the civilian's leg was injured, and it looked like Ladybug was on the back foot, defending a target with limited mobility without her usual partner.
After seeing that, there was no question as to what a hero would do.
The silver-armored villain with a sword apparently attached to her hand made to lunge at Ladybug and the civilian she was protecting, and the hero known as Deku flexed his muscles and cried out.
"One for All! FULL COWLING!"
A green blur intercepted the villain, taking her by surprise as her sword's lunge was deflected skyward before the interloper planted a fist in her stomach, sending her flying backward into a chimney and stunning her.
The villain wasn't the only one who was stunned by his actions, as Ladybug and the boy she was defending looked at Deku with wide eyes and dumbfounded expressions. "W-What the-" Ladybug spluttered out as Deku allowed his Full Cowling to fade for a moment now that the immediate danger was taken care of.
Riposte managed to gather herself fairly quickly given how hard she had been struck, and leveled her sword in Deku's direction, a fierce look directed at the interloper. "I don't know who the hell you think you are, but this fight is between me and Agreste! Ladybug interfering is one thing, but you have no business meddling here!"
Deku couldn't help the snicker that welled up from within him; a snicker which quickly turned into full-bodied laughter. His reaction caused a look of confusion from everyone else on the rooftop, and a snarl of anger from Riposte within a few seconds.
Eventually his mirth died down, and he smiled at the girl who became his opponent because of a little butterfly. "Ah, didn't anyone ever tell you, villain?" He asked. "Meddling where you have no business… is the essence of being a hero." His gaze turned intense as he took a fighting stance. "And no matter what happens, I will always try my best to live up to the name of 'Hero.'"
The expression of the villain before him turned furious, and she tensed up, prepared to lunge at this new obstacle in her way. Ladybug finally found her voice again as things became dangerous. "No! You shouldn't put yourself in danger like that! It's not your job to have to deal with these villains; Chat Noir and I are the ones with superpowers, so we should be the ones to handle this!"
"No need to worry about me, Ladybug," Deku replied, glancing backwards at the heroine. "You and Chat Noir aren't the only ones with powers, actually." He didn't see the look of shock on Ladybug and Adrien's faces as he turned to face Riposte once more. "Hawk Moth. Although I haven't been able to act until now, I haven't come into this fight without any preparation. It's obvious from the research I've done on past incidents that you have at least some awareness of the things happening around the people whom you've corrupted."
The butterfly mask appearing over the face of his opponent, outlining her features in purple light, told Deku that Hawkmoth was now listening intently. "So, I have a message for you, the real villain behind all of this." His fists clenched and his expression turned intense again. "Ladybug and Chat Noir have a new ally! A new hero who won't stop until your evil actions come to an end, and the innocent people of this city can be free from the fear of being turned into tools for your greed! I am Deku! The hero who puts all his effort into everything he does! I will see your villainy brought to an end, Hawk Moth!"
The mask of purple light remained over Riposte's face as she responded. "You won't stand in my way, or the way of Hawk Moth's goals, 'Deku.' You're just another insignificant obstacle that will be overcome!" With these words, she lunged forward, sword hand raised to strike down the hero before her.
Deku met her attack with a lunge of his own, green lightning crackling around him as he directed the power of One for All through him.
"One for All… Texas… SMASH!"
Putting all his might into this action, Deku swung his fist toward his opponent, a smile on his face as he finally fought to protect the innocent once again.
A/N: I am now out of alcohol and out of motivation. Let me know what you think, and maybe I'll keep getting drunk and letting my nonsense plot bunnies leak onto this website. Laters.