A/N: So this is my first ever story so I can't really promise outstanding quality or anything (I'll try my best though). A crossover I'd recommend pertaining to these two franchises would be "Footwork" by herecomestheboom.
For a bit of background info, this story branches off the game Sonic Forces, with the point of divergence being the final battle with Infinite. Also, in this continuity at least, Chaos Control can be performed without a Chaos Emerald in hand, it's just less powerful and strenuous.
Also, unsurprisingly, I don't own Sonic, My Hero Academia, or any of the characters or concepts pertaining to it. So uh, don't sue (Please?).
...
Things were finally looking up.
In response to a powerful blow, Infinite, a masked Jackal wielding the power of the Phantom Ruby, reeled back in pain, dragging his feet across the ground in an attempt to keep his footing. The attacks being dealt struck him with such speed and force that his mask nearly flew off his face. He grasped the Phantom Ruby embedded at the center of his chest, visibly bruised and strained. While the mercenary radiated a menacing aura, under his mask he was breathing erratically and sweating profusely.
Before him stood Sonic the Hedgehog, the Hero of Mobius, and a Mobian wolf who went by the nickname "Rookie" and wielded a "Burst Wispon". The two had met on the Death Egg when the Rookie sought to save Sonic from the clutches of the Eggman Empire, forming an unbreakable bond. Joining forces with Sonic, they waged war as the two primary agents of the Resistance, freeing the world of Dr. Eggman's ambitions. Now facing Infinite at the Eggman Empire Fortress, the war was coming to a close.
"Here goes, partner!" Sonic chirped, "When we join forces, the sky's the the limit!"
"Double Boost!"
Joining hands, the duo propelled beyond the sound barrier and formed a blue energy aura around themselves, impacting their adversary head-on. The force of the attack caused a massive shockwave that surged throughout the area, launching Infinite far away. The mercenary landed with a thud, and it sounded like something broke.
...
"No, wait! I can still... fight!"
That was all the cornered Infinite managed to say before seemingly fading from existence against his will, much to the confusion of Sonic and the Rookie.
Before the mercenary seemingly vanished into thin air, Sonic had gone on a cheesy spill about his his teamwork and synergy with the Rookie won the day, ready to subdue his "ultimafe" foe and end this war once and for all. It's been a good while since he's gone all out, so he was wondering if he had accidentally killed his adversary.
"So um..." Sonic spoke,"That isn't a good sign."
Before anything else could be said, the ground began shaking violently. Sonic let out an exasperated 'there it is' as a gigantic robot emerged from the metallic floor in front of the heroes. Sonic had to step back a bit fully view the titanic machine.
A giant battle robot over a hundred feet tall loomed over the heroes. It was a humanoid mech suit with a round body, a blue and red color scheme, and its right hand consisted of a large spiked ball. Its facial features consisted of a spikey mustache, sharp teeth painted in a permanent frown, and green eyes.
"Jeez Egghead," Sonic mocked, "Did you just throw this soon-to-be scrap heap together at the last minute? I'll tear this thing apart in under-"
Moving at surprising speeds, the robot closed the distance between itself and the heroes. While Sonic was able to bolt out the way at the last second, the Rookie received a metallic boot to the face, knocking him several meters away and rendering him unconscious. The machine didn't relent there, turning to the hedgehog and swinging its spiked ball persistently like a flurry of bullets. Sonic was able to narrowly evade its blows, but quickly decided to go on the offensive, barreling into the robot's chest in order to knock it several yards back and give him a bit of breathing room. Having a brief window to act, Sonic quickly turned to check on the Rookie, kneeling to his unconscious form to check his pulse and heartbeat.
"Still breathing..." Sonic muttered in relief. He cradled his partner in his arms and was just about to make a tactical retreat until...
"Not so fast!" His egg-shaped adversary threatened, lunging towards the pair.
"Chaos Lance!" A familiar voice shouted.
In a bright red burst of energy, the giant machine was sent reeling backwards, this time with visible damage to its chest area.
A menacing figure suddenly jumped between Sonic and the robot. The attacker, Shadow the Hedgehog, was enveloped in a red aura of Chaos Energy, indicating his Chaos Boost technique was active.
"Bring as many rabble as you like!", The villain spat angrily, "This Egg Breaker is invincible!"
Shadow took a moment to size up the "Egg Breaker". It looked like something he could take apart with moderate difficulty at most, but Shadow knew it was never that simple. He turned to his blue ally, and emerald-green eyes stared back, accompanied by a familiar toothy grin that Shadow knew and loathed.
"What took ya so long, Faker?" Sonic chirped.
"Tell me, Sonic, what are we up against?" Shadow asked flatly, practically ignoring Sonic's remark.
Sonic shrugged, "Your guess is as good as mine. We took down the masked clown, then Eggman catches us off guard with this thing. All I know is that it's a lot tougher than your typical Badnik."
"Unfathomably 'tougher'!" Eggman gloated, "This here robot is supercharged by the finalized Phantom Ruby." Shadow grimaced for a moment before composing himself. That would make things a bit more... difficult.
"More are on the way.", Shadow stated, "They're a bit caught up with the Doctor's forces, but going by how smoothly the battle is going they'll be here any minute." Sonic was pleased at the news, but then gestured toward the Rookie with a concerned look. Shadow nodded and snapped his fingers, warping the wolf to from the battlefield via Chaos Control.
Sonic stood to his feet proudly, and began stretching. "Hang back, Shadow. Eggman's mine."
In a flash of golden light, Sonic's form was radically altered. The blue hedgehog's fur morphed into a brilliant gold color, his eyes became a glowing ruby red, and his quills pointed upward. Super Sonic clenched his fists as he began floating upward, an arrogant grin plastered across his face.
"You had the Chaos Emeralds?!" Eggman cried, mouth agape. Shadow was caught off guard as well, his eyes widening in shock.
"Slipped into the Special Zone right after I escaped the Death Egg." Super Sonic explained. Shadow simply rolled his eyes, stepping out of his way as the Doctor was fuming from inside his mecha.
The Egg Breaker bolted towards Super Sonic at top speed, a menacing red aura surrounding it. It brought its spiked ball on the golden figure.
"Game over, Eggman."
Eggman's jaw dropped as he witnessed what took place before him.
Super Sonic had the robot's spiked ball effortlessly gripped in his hand. The Egg Breaker attempted to rip out of the hedgehog's hold, but was unable to budge an inch out of his grasp.
"Yoink."
With one swift movement, Super Sonic ripped the robot's arm out of its metallic socket. He quickly tossed the tons worth of solid steel aside as if it were a sack of potatoes.
"Need a hand?" Super Sonic quipped snidely. The Doctor used the Egg Breaker's remaining hand to slug the super-powered teen, thrashing the hedgehog with his colossal fist. Of course, Super Sonic didn't feel a thing.
"You know you can't win, right-"
"Don't sass me, you miserable, insufferable, brat!" Eggman suddenly shouted at the top of his lungs. Caught off guard, Sonic was going to brush it off with more snarky comments, but the Doctor continued his rantings. "I had this whole planet in the palm of my hand, but here you go ruining things at the last possible moment AGAIN!!"
This was different from the Doctor's typical rantings. While he'd usually confidently dismiss his defeats as mere "setbacks" and go on about how'd his next plan would surely win the day, this time he sounded utterly pissed. And a bit... unhinged?
The Doctor threw another fruitless strike at the hero, leaving him unscathed as per usual. Everyone and their mothers knew Super Sonic was practically immune to physical harm, even shaking off attacks from Gods capable of wiping out the entire world. So why was Eggman going for such counterproductive attacks? Why not use one of the Phantom Ruby's many and very, very annoying abilities?
"Doc-" Sonic opened his mouth to say something, this time sounding sympathetic. But the Doctor just kept on going.
"I've beaten you before, rodent!" Eggman gloated, "I can do it again!" The Egg Breaker's aura radiated a bright red glow, which rapidly expanded into a powerful blast of energy that engulfed the golden teen. It's sure as heck didn't hurt, per se, but Super Sonic seemed to stagger backwards in shock. The blast of energy was continuous, engulfing Sonic and gradually expanding in size and intensity. Shadow was aware that the energies of the Phantom Ruby were dangerously unpredictable, so he didn't take kindly to Sonic dragging the battle out the way he was. He couldn't destroyed the Doctor's machine the moment he went "Super". Hell, he could've ended this whole damn war if he truly had the Chaos Emeralds for that long.
"Sonic, end this!" Shadow commanded. The hedgehog's cries fell on deaf ears as his golden rival was bathed in the mysterious energies of the Phantom Ruby, clashing with the Chaotic energies that coursed throughout his form. Sure, the blast wasn't strong enough to hurt Super Sonic, but the combination of the supernatural energies destabilized Sonic's Super State. Sonic felt like he was being unraveled from the inside, with the world going blank from his perspective.
Without thinking, Shadow tossed a Chaos Spear at the Egg Breaker, and what resulted was a massive "glitch" that surged throughout the area. The "glitch" distorted the fabric of reality, inverting all colors in the vicinity.
"Sonic!" Was all that as heard as the "glitch" subsided.
As the "glitch" cleared away, there was nothing. No heroic hedgehogs, no killer robots, no magical gemstones. Just silence.
...
Things weren't looking too hot.
Three students shuddered as they peered from the waters of the Unforeseen Simulation Joint, practically frozen in fear as they watched the gruesome scene that played out before them. Blood drenched the floor as face met concrete; agonized screams filled the air as bones snapped like twigs. The source of this immeasurable pain was Noumu, the bio-engineered trump card of the so-called "League of Villains". The villain had Shota Aizawa, or Erasure Hero: Eraser Head, pinned to the ground. The villain seemed intent on breaking every bone in the hero's body as slowly and painfully as possible with his ridiculous strength.
Izuku Midoriya was petrified, feeling completely helpless. His classmates, Minoru Mineta and Tsuyu Asui, were in the same boat, looking as if they were going to faint. With every grating crack of bone and pained scream they felt as if they were going to lose their lunch.
They had initially visited the USJ with intent to partake in some disaster training, with the facility having eight sections, each emulating a certain environment. Things took a turn for the worse when numerous villains appeared out a black fog and expressed ambitions to kill the Symbol of Peace. The black fog, which was actually a villain with teleportation Qurik, scattered the students of Class 1-A across the USJ, forcing the Heroes-in-training to fight for their lives.
"I can't watch this anymore..." Mineta whimpered, "Shouldn't we be booking it out of here?"
Mineta's words fell on deaf ears as Izuku spaced out, his eyes glued to the agonizing scene. Suddenly, a famililar black fog appeared out of no where, grabbing Izuku's attention. Kurogiri addressed the ringleader, Tomura Shigaraki. Izuku didn't pick up on their entire conversation, but it seems like Kurogiri brought news that agitated Tomura, causing him to scratch violently at his own neck. The Decay Quirk user was growling and panting heavily as if he was having a mental breakdown.
"Kurogiri... you idiot...". He spat, angrily fidgeting. If looks could kill Kurogiri would be a smothering pile of ash. "If you weren't our warp gate, I'd tear apart every last atom in your body."
The Decay villain abruptly composed himself, addressing the situation in a reasonable (ish) manner. "We can't win with dozens of Pros jumping down our throats. It's game over. Back to the title screen."
Suddenly, Tomura looked dead at the terrified students, his bloodlust apparent through his stare. Izuku felt his heart sink.
"But first, let's make sure the 'Symbol of Peace' is broken." Moving faster than the eye can see, Tomura closed the distance between himself and Asui, reaching out in attempt to use his deadly Quirk. "Let's make this hurt".
Everything seemingly slowed to a near-halt as a terrible sense of dread washed over Izuku. The student recalled what the villain's Quirk withering his teacher's elbow, and winced at the thought of the same happening to his friends. Acting on instinct, Izuku was going to leap from the waters and repel the fiend with an all out attack.
And then, time literally froze. All colors in the vicinity seemingly inverted as the world came to a stop.
"Move." A Black Wind tackled into Tomura, knocking the Villain several yards away. The universe resumes as Tomura falls flat on his ass, ready to slaughter whatever dared to impede him.
"Another brat." Tomura hissed, contempt oozing through his tone. Before him stood a young, annoyed looking teenager with a lean build. He had long, sharpened, quill-like locks of hair with black and red stripes. His attire consisted of a plain white t-shirt, and a black and red jacket and shorts. He also had weird-looking shoes, fingerless gloves, and wore golden Rings around his wrist. Tomura could tell just from a glance that this kid was the dark and gloomy type. He couldn't care less at the moment though; he just wanted him dead.
"Nomu, splatter him across the floor" Tomura ordered, beckoning towards the newcomer. The instant the command registered, the Villain left the beaten and broken Aizawa and bolted toward the newcomer, a fist cocked back ready to punch the teenager's head from his shoulders.
"Chaos Control."
After the gloomy teenager uttered these words, he disappeared from sight. Moments later, the teenager reappeared behind Nomu, now armed with what appeared to be a red ball of light. He hurled the sphere at the monster, knocking it to the floor in a bright burst of light. Viewing this, Tomura's blood boiled.
"What... are you!" Tomura demanded. The teenager turned to him, looking throughly unimpressed.
"I'm Shadow the Hedgehog." Shadow introduced, "I refuse to stand idly by and allow you to murder these children. I'll destroy you first."
Shadow then diverted his attention to Nomu, who got back to its feet without a scratch on it. "I put everything I had into that attack.", Shadow thought. He quickly considered hit and run tactics in conjunction with piercing attacks, assuming raw force wouldn't faze the creature. Giving Nomu a determined glare, Shadow braced himself and waited for it to make a move.
Seeing the child's resolve only served to piss off Tomura even more. This child's fearless demeanor reminded him of a certain Symbol of Peace that he came here to knock down a peg. Though whereas All Might would simply proclaim he'd stop their endeavors, this brat was arrogant enough to suggest he'd kill the Villains. He even somehow mustered enough force to knock his trump card to the floor. How... troublesome.
"Well, at least we'll have enough time to kill this kid before any Pros-"
And then, the door of the USJ exploded.
...
Shadow tilted his head in confusion. Mere moments ago, these children were stricken with fear, feeling helpless in the face of danger as these Villains came pretty damn close to claiming their lives. Now they were grinning like idiots just because one man showed up. How would this unarmed, ill-prepared man improve their situation?
"Have no fear, students.", The man spoke with an inspiring sense of resolve, "I am here."
"He's here... All Might" Izuku gasped, tears swelling up.
All Might began walking forward, removing his coat.
"I couldn't shake the feeling that something was wrong here when Aizawa and Thirteen didn't answer my calls." All Might explained, "So I hurried over, running into Young Iida alongside the way. He told me of the villiany at work here."
All Might continued to stride confidently, surveying the ruined USJ. He proceeded to rip away his necktie, a scowl directed at the soon-to-be floored lowlifes.
"Idiots, don't hesitate!", One of the lowlifes shouted, "If we strike now, we can-"
Moving at blinding speeds, All Might bolted towards a group of criminals and struck them down with incredible ease. He didn't stop there, proceeding to grab the unconscious Aizawa before the Villains could hope to stop him. He grimaced as he looked over his battered form.
"I'm sorry, Aizawa.", All Might said with a frown, "I should've been here."
Moving at ridiculous speeds yet again, All Might snatched the students from Tomura's reach.
"Everybody, back to the entrance. I'm leaving Aizawa to you."
"I see.", Shadow mused, "This man appears to have a superhuman physique." Shadow wasn't particularly impressed by the man's speed yet. Though he had a strange feeling that he would be eating his words in a moment.
Judging by everyone's relieved expressions along with this man's demeanor, abilities, and ridiculous name, Shadow deduced that this was some sort of superhero. Hopefully he didn't conduct himself in a manner similar to a certain blue oaf.
Turning to Shadow, All Might gives the teenager an unsure look before addressing him. To his confusion, he didn't recognize the child, but could tell that he wasn't siding with the Villains. "That means you too, Young one. It's time to get to safety and leave this to the professionals."
Shadow simply raised a brow at the hero. Sure, he seemed capable enough. But that 'Noumu' thing was immune to physical blows, which seemed to be All Might's only method of assault. Shadow's Chaos Powers and (presumably) far greater speeds were a perfect counter. Strategy aside, who the hell does this man think he is?
"Who are you to command me?" Shadow retorted, slightly offended. All Might gave the speedster a skeptical look. Insubordination aside, did this teenager not have any faith in the Symbol of Peace?
All Might spoke sternly, "Listen here. This situation is already bad enough without-
"Nomu, finish him already!" Tomura interrupted, his blood boiling.
With a shrill shriek, Nomu bounded towards Shadow, ready to end the speedster's life with a full power punch. Right in a nick of time, All Might pushed the teenager aside, taking the full impact of the blow. The collision caused a powerful shockwave that surged throughout the area, causing Shadow and several onlookers to lose their footing. When the carnage died down, it was revealed that All Might was able to block the attack, albeit he did seem very strained.
"That power...". Shadow gasped, "I... definitely wouldn't have been able to withstand that."
Shadow quickly got to his feet, still fully prepared to throw down. He still had a few tricks up his sleeve.