The smell of the place was the first thing that hit Yu. It was a mixture of superheated metal, damp concrete, and the sharp scent of rust. It was definitely not the clean, almost antiseptic air of the U.A. facilities, not even the gym Izuku had initially secured.

“I’m sorry, Takeyama, but the reviews were five stars,” Izuku had tried to explain that morning, showing her his phone. “It said ‘spacious and with excellent ventilation.’ It didn’t specify that the ventilation came from a hole in the ceiling and that the space was shared with a senior citizens’ yoga class.”

“Midoriya, I almost crushed a woman who was in warrior pose,” Yu retorted, crossing her arms. “She kept telling me my ‘aura’ was a ‘chaotic color.’ It was humiliating.”

It was then that Mirko, who had been listening with a mocking grin, snatched the phone from Izuku. “Let me handle it. I know a place. An old friend owes me a few favors.”

And now here they were, in the industrial bowels of the city. A warehouse so vast its ceiling was lost in shadows, supported by a web of steel beams that looked like the skeleton of a colossal whale. The concrete floor was covered in scars: craters of various sizes, fissures that spread like spiderwebs, and deep scorch marks that told stories of past battles. Scattered across the space were enormous concrete blocks, shipping containers stacked like a giant child’s toys, and a jungle of pipes and scaffolding.

“Welcome to the ‘Dome of Destruction’,” Mirko announced, a wild smile on her face that seemed perfectly at home in this environment. Her voice echoed in the silence of the place. “Nobody here will ask questions about collateral damage. You can get as big as you want, Takeyama. You have no excuses to hold back.”

Yu swallowed hard. The air felt heavy in her lungs. She felt small and insignificant in the vastness of the place, and that was before activating her Quirk. The determination she had felt in her apartment, that spark of confidence, now felt like a distant memory, replaced by a growing wave of dread. This was Mirko’s territory. Every surface was a launchpad for her, every shadow a place to hide.

Izuku, on the other hand, looked like a kid who had just walked into the world’s biggest candy store. His green eyes shone with an almost feverish intensity as he spun around, taking it all in.

“Whoa…” he muttered, his voice echoing slightly in the cavernous space. “This is incredible. The tactical possibilities are nearly endless. The containers create perfect blind spots, the scaffolding offers multiple levels for vertical attacks, and the scattered concrete blocks can be used as destructible cover to change the battlefield in real-time. You could even use the echo to disorient an opponent with a sonic Quirk!”

“Exactly, short stack,” Mirko said, clapping him on the back so hard it nearly knocked him over. Izuku stumbled but caught his balance with surprising agility. “And the first tactic we’re going to test is seeing if pretty girl knows how to throw a punch without being sixty feet tall.”

She turned to Yu, her smile vanishing, replaced by a predatory gaze that made Yu’s skin crawl.

“You and me. No gigantification Quirks. Let’s see what they really taught you at the academy.”

Yu felt a knot form in her stomach. She knew she was a decent fighter in her base form. She had passed her exams, had good grades in hand-to-hand combat. But Mirko… Mirko was a force of nature. It was like comparing a house cat to a wild tiger.

“Aren’t we going to warm up first?” Yu asked, trying to buy some time, her voice sounding weaker than she intended.

Mirko’s smile returned, sharp as a knife. “Warm up? Panic is the best warm-up. You ready to cry, rookie?”

She dropped into a low, elastic combat stance, bouncing lightly on the balls of her feet. She was the picture of contained energy, a coiled spring about to explode. Before Yu could even form a coherent response, the rabbit hero launched herself forward.

What followed was a blur of pain, confusion, and humiliation. Yu barely had time to raise her arms to block before the first blow landed. It wasn’t a punch, but a swift, hard kick to her thigh that instantly made her leg go numb. The impact resonated through her entire body like a sledgehammer blow.

Too slow! Yu thought, as she tried to counter with a right cross. But the space where Mirko had been was now empty. She felt a dry impact on her back, right between her shoulder blades, that sent her stumbling forward. Before she could regain her balance, a precise sweep hooked her ankle and sent her face-first onto the dusty concrete floor. The impact knocked the wind out of her, and the taste of dust and metal filled her mouth.

She pushed herself up, coughing, her jaw tight. Okay, she’s fast. I have to anticipate, not react.

She faced Mirko again, who was simply waiting for her with an almost insulting patience. Yu threw a jab, followed by a cross, aiming for where she thought Mirko would move. But the hero didn’t move sideways. She ducked under the punches with impossible fluidity and landed three quick, stinging blows to Yu’s abdomen. They weren’t knockout punches, but hits designed to demoralize, to steal her breath and her focus.

“Come on, pretty girl!” Mirko taunted, dodging a clumsy hook with a simple bob of her head. “My grandma hits harder! Is that all you’ve got? Your footwork is a disaster. You’re planted on the ground like you’re waiting for roots to grow.”

“Shut up!” Yu growled, frustration beginning to cloud her judgment. She lunged forward in a desperate flurry, a series of punches that met only air. It was like trying to hit smoke.

Mirko slipped around her, a white blur of relentless motion. “I’m getting bored!” she sang. Yu spun, trying to track her, only to be met with a spinning kick that connected cleanly with her ribs. The pain was sharp and white, and the air left her lungs in an audible hiss. She doubled over, unable to breathe.

Finally, Yu was on the ground, on her hands and knees, panting. Sweat plastered her hair to her forehead and temples. Tears of pure frustration stung her eyes, but she refused to let them fall. It had been a total, absolute, one-sided beatdown. She hadn’t even come close to touching her. Every move she made, every strategy she tried to formulate, Mirko was already three steps ahead.

A pair of worn, familiar red sneakers entered her field of vision. Izuku knelt beside her, his face unusually serious. Yu braced herself for a barrage of cold analysis and data about her failure. She expected to hear about her reaction time and a detailed breakdown of every mistake she had made.

But Izuku’s voice, when he spoke, was surprisingly gentle.

“You were overthinking,” he said, not a trace of judgment in his tone, just calm observation. “Right before you threw that last combination, I saw you hesitate. Your shoulder tensed, but you stopped for a split second. You were looking for the perfect opportunity, the flawless moment to strike.”

Yu didn’t answer, too ashamed to look him in the eye. She just stared at a crack in the concrete.

“Against an opponent like Mirko, the perfect opportunity doesn’t exist,” he continued. “She’s not going to give it to you. You have to create it. Force it. Even if the punch isn’t perfect, it forces her to react, and in that reaction, you can find your real opening.”

The silence stretched for a moment, broken only by Yu’s ragged breathing.

“When you feel cornered,” he added, his voice barely a whisper, “you reach for your Quirk like a life raft. I can see it in your eyes. Behind every punch you miss, there’s a thought: ‘If only I could get big.’ But what happens when you can’t use it? When the environment doesn’t allow it, or when the villain is too fast? You drown.”

His words hit her harder than any of Mirko’s kicks because they were the naked truth. Her Quirk was her identity. She was Mt. Lady. It was her power, her confidence, her everything. Without it, she felt weak, exposed, incomplete.

“Your foundation is fragile, Yu,” he concluded, using her first name for the first time. The sound was strangely intimate in the starkness of the warehouse. It made her look up. “And that’s the first thing we’re going to fix. But for now… we’re not done. Get up.”

She looked at him, confused. “Get up? For what? So she can use me as a punching bag again?”

“No,” he said, a small smile tugging at the corner of his lips. “Get up and remind her why they call you Mt. Lady.”

A fresh wave of adrenaline shot through her, mixed with a stubborn defiance. She got to her feet, her legs trembling from the effort and the impacts, and activated her Quirk.

The sensation was, as always, intoxicating. The world shrank around her as she grew, the containers becoming shoeboxes, the scaffolding fragile cages. The warehouse ceiling, once lost in the shadows, was now at shoulder height. The pain in her ribs and thighs vanished, drowned out by the immense feeling of power that flooded her.

Mirko, now a small white figure on the ground below, looked up and grinned widely. There was no fear on her face, only pure, predatory excitement.

“That’s more like it!” she yelled, her voice booming off the walls. “Now this is a real fight!”

The battle changed drastically, but not in the way Yu expected. Now she was the one with overwhelming power, and Mirko was the gnat. But she was the most dangerous, cunning gnat in the world. Yu tried to swat her with a blow that would have pulverized a car. The strike came down with the force of a hydraulic press, but Mirko was already gone. She had leaped, bouncing off a container and then a wall, dodging the impact with insulting ease. Yu’s fist smashed into the concrete, kicking up a cloud of dust and sending shockwaves through the floor.

“You’re gonna have to be faster than that, giant!” Mirko shouted from atop a stack of containers.

The fight became a large-scale game of cat and mouse. Yu destroyed the environment trying to catch the speedy hero. A missed punch brought down a scaffold, which Mirko immediately used as a new series of platforms to launch herself from. A stomp meant to trap her only created a crater that Mirko shot out of at an unpredictable angle. She was using the debris Yu herself created as new weapons and escape routes.

Despite her size, Yu managed to land a few indirect hits. She didn’t strike her directly, but the force of her near misses created shockwaves that forced Mirko to dodge and reposition. A couple of times, she almost caught her, feeling the displaced air from her fingertips brush against the hero’s suit. It was exhausting, physically and mentally. Moving that much mass with precision required immense concentration.

Finally, after a particularly clever move, Mirko lured Yu into a corner of the warehouse. Yu, thinking she had her trapped, threw a sweeping sideways blow to take her out. But it was a trap. Mirko bounced off the back of Yu’s hand just before impact, launched herself onto a remaining scaffold, and from there, at the apex of her jump, she dove. She came down like a white missile, striking the back of Yu’s knee with an axe kick of incredible force.

Yu’s leg buckled with a metallic clang and a groan of over-strained tendons. She fell to one knee with a crash that shook the entire building. The lights on the ceiling flickered from the impact.

She stayed there, panting, the fatigue weighing on her like a mountain. She placed a gigantic hand on the floor to steady herself. She saw Izuku approaching her, his notebook in hand, probably to detail her new, colossal failure. She prepared for another round of analysis.

“Yu,” he said, his voice strangely calm as he stopped beside her. He was so tiny she had to tilt her head to see him properly, a small green-and-black figure next to her knee. “I need you to trust me. Just for a moment. Don’t move.”

Before she could ask what he meant, or even process the request, he moved. Not with Mirko’s speed, but with a quiet, determined efficiency. He simply took a step toward where she was now kneeling and, with a naturalness and a lack of hesitation that left her completely paralyzed, placed both of his hands on her rear and held on.

It wasn’t a hit, or a playful pat. It was a firm, deliberate, almost technical grip. His fingers molded to her form through the spandex of her suit, squeezing with a clear, focused intention that was anything but lewd, yet undeniably physical. Yu’s mind went blank for a second. The logical circuit that processed social behavior, personal boundaries, and basic physics simply shorted out. She couldn’t comprehend the audacity, the absolute violation of every unwritten rule.

“WHAT THE–?!” she screamed, her voice a thunderclap of indignation that made the remaining glass in the highest windows vibrate.

But her shout was drowned out by the sensation that flooded her. It was instantaneous and overwhelming. Like liquid solar energy had been injected directly into her bloodstream. A deep, vibrating warmth spread from the point of contact, an electric hum that coursed through her legs, surged up her spine like a tide, and reached the tips of her fingers. The fatigue that had been crushing her vanished in an instant, replaced by a clarity and strength she had never felt before. Her muscles, which had been burning with effort, now felt like taut steel cables, filled with limitless power.

She felt Izuku’s hands and body pull away.

“Now!” he yelled from the ground, his voice filled with a feverish urgency that cut through the fog of her confusion. “Get up and fight! Use that energy!”

Driven by a strange mix of pure rage at what he had just done and this bizarre new surge of power, Yu leaped to her feet. The movement was so fast and explosive it surprised even her. She looked at Mirko, who was watching from across the warehouse with a raised eyebrow, and roared. She charged forward, not with her previous clumsiness, but with a speed and agility she had never possessed in her giant form.

Mirko, visibly surprised by the sudden burst of speed, jumped to dodge. But Yu’s punch was so fast that the shockwave caught her in mid-air, destabilizing her. For the first time in the entire session, Mirko had to land awkwardly, rolling across the ground to dissipate the momentum.

She sprang to her feet, a grin of pure combat joy on her face.

“THAT’S IT!” the rabbit hero yelled, brushing some dust off her shoulder. “THERE IT IS! COME ON, HIT ME IF YOU CAN!”

The battle continued, but now it was a true duel. Yu still couldn’t catch Mirko, but the difference was night and day. Now she was forcing her to go all out, to use her full skill to avoid her newly empowered, swift attacks. Yu’s punches were more precise, her movements more fluid. She was no longer just reacting; she was anticipating, cutting off Mirko’s escape routes and forcing her to make split-second decisions.

When Izuku finally called the session by shouting, “Time’s up!” both sides were completely exhausted. Yu shrank down, the sudden power leaving her. She landed softly on her knees on the floor at her normal size, breathing heavily, every muscle in her body trembling. Mirko, some distance away, was leaning against a wall, her chest rising and falling rapidly, but with a huge, satisfied grin on her face.

Once she caught her breath and the feeling returned to her lungs, Yu’s rage, which had been supplanted by the concentration of combat, returned in full force. She stood up, ignoring the pain, and marched directly toward Izuku. He had his back to her, diligently writing in his notebook, oblivious to the storm approaching him.

With a snarl, she snatched it from his hands.

“Let’s see what brilliant analysis you made of… of…!” She stopped short, her eyes scanning the latest notes. Her face went from red with anger to pale with shock in a matter of seconds.

She read aloud, her voice trembling with disbelief.

“‘Note: Direct Quirk application with intent of ‘strength enhancement’ is successful. The rear area in giant form is much more comfortable than in her normal version… I wonder if in the future she could pay me by letting me sleep on her butt, it’s comfortable.'”

She paused, swallowing hard, her eyes moving frantically to the next line.

“‘Elasticity level: outstanding’? ‘Rebound factor on impact: impressive’? ‘Curvature defies conventional anatomical expectations’?! ‘Firmness level: comparable to a high-performance tire but with the softness of a luxury dessert’?!”

She looked up at him, her eyes wide, the notebook trembling in her hand.

“THIS ISN’T ANALYSIS, IT’S A PERVERTED POEM! I THOUGHT YOU WERE TAKING COMBAT NOTES!”

An explosive sound, a choked gasp followed by a snort, interrupted her tirade. It was Mirko. She had snuck up on them and was now bent at the waist, howling with laughter. She was clutching her stomach, tears streaming from her eyes as she struggled to breathe.

“AHAHAHA! Oh, I can’t… I can’t breathe! ‘Luxury dessert’!” she managed to get out between laughs. “That’s pure gold, short stack! GOLD!”

After calming down a bit, wiping a tear from the corner of her eye, she looked at Izuku with a new level of interest, a spark of manic curiosity in her gaze.

“So, you little pervert,” she said, her voice still shaky with laughter. “That trick… does it work on anyone? Or just those with a ‘show-quality’ rear end?”

Izuku, who seemed completely unfazed by the accusation, looked at her with total seriousness. “The hypothesis suggests it would work on any part of the body. The intent is the key, not so much the area of application, though a larger surface area might facilitate a more stable energy transfer.”

Mirko grinned, a dangerous and exciting idea forming in her mind. “My legs are pretty well-developed. They’re my main asset. What can you do for them?”

Izuku nodded, as if it were the most normal, scientific request in the world. “Get into a jumping stance. I’ll analyze the effect on explosive muscle propulsion.”

Mirko obeyed instantly, crouching slightly, the muscles in her legs tense and defined. Izuku knelt and placed his hands on her powerful thighs. Yu watched the scene with a sense of total unreality, as if she were in a fever dream. Mirko didn’t seem embarrassed in the slightest; she was expectant, almost vibrating with anticipation. Izuku concentrated for a moment, and Mirko let out a sharp hiss.

“Oh… whoa. That’s… an interesting tingle. It feels like… static electricity building up directly in the muscle.”

“Try it now,” Izuku said, removing his hands and stepping back.

Mirko grinned. And jumped.

It wasn’t a jump. It was a launch. She shot up and forward like a white rocket, a blur that crossed half the warehouse in the blink of an eye. Her cry of surprise was drowned out by a deafening CRASH! as she slammed into the far wall. She tore through a sheet of corrugated metal like it was tissue paper and left a car-sized dent in the thick concrete behind it.

There was a moment of stunned silence. Yu and Izuku stared at the cloud of dust and debris.

“Mirko!” Yu yelled, genuinely worried.

A wild, euphoric, and completely unhinged laugh echoed from the other side of the warehouse. Mirko rose from the rubble, her suit a little torn but seemingly without a scratch. Her eyes were wide with pure adrenaline.

“AHAHAHA! I FELT THAT! THE ACCELERATION! IT WAS INCREDIBLE!” She pointed a trembling finger at Izuku, her entire body buzzing with energy. “YOU! I WANT MORE!”

She strode toward them, her energy vibrant and chaotic. She looked at Izuku with a mixture of awe and an almost reverential respect.

“Short stack, I don’t know what the hell your Quirk is, but it’s insane. It’s the best drug I’ve ever tried.”

She pulled the business card he had given her from her belt and then her phone. With surprising care, she entered the number.

“We’re in touch,” she said, putting the phone away. “Very in touch. If you ever need a testing ground, or someone to experiment on the limits of that power with, you call me. Any time. And you,” she said, turning to Yu, her tone now a strange mix of mockery and newfound respect, “you’re not bad, Takeyama. You were a punching bag today, but you had some bite at the end. If you stick with the kid and his ‘luxury dessert analyses,’ you might stop being so boring.”

With one last predatory grin, Mirko left, leaping through the hole in the wall she had just created, leaving a trail of destruction and confusion in her wake.

Yu and Izuku were left alone in the vast, now-silent dome, surrounded by the debris of their training. Yu was sore, exhausted to the bone, and her brain felt like it had been blended and reconstituted several times in the last hour. She looked at the boy beside her, the boy who had humiliated her, made her stronger, written an ode to her butt, and had just turned the number five hero into an addict for his power.

She didn’t know whether she wanted to kill him or thank him.

“Midoriya,” she finally said, her voice hoarse with exhaustion.

“Yes?” he replied, having already retrieved his notebook and making a new entry.

“We need to talk about your… training methods. Specifically, the ones that involve unsolicited physical contact.”

Izuku looked up, blinking, as if the idea that this was a problem was completely foreign to him.

“Of course. We should analyze the data from the session. The energy transfer was considerably more efficient in your giant form, likely due to the increased surface area and the… tissue composition. I’ll have to investigate if different body parts offer different conductivity…”

Yu just let out a long, deep groan of frustration and let herself fall backward onto the dusty concrete floor, staring up at the distant, dark ceiling. This was going to be a very, very long collaboration.