My Hero Academia: The Hidden Pulse

Kairo arrived at Training Hall 3 before dawn. The air was cool, the sky still shrouded in darkness. The campus was silent, save for the rhythmic hum of security drones patrolling the grounds.

Mei Hatsume stood near the entrance, arms crossed, a sly smirk on her lips. Unlike most students, she looked completely awake.

"You're actually serious about this, huh?" she asked, tilting her head.

Kairo rolled his shoulders, warming up. "I wouldn't be here otherwise."

She whistled. "Most people wouldn't come back after the last time."

Kairo smirked. "Most people aren't me."

Mei chuckled and adjusted her gloves. "Alright, let's see if you can handle this."

She snapped her fingers—and the world changed.

Illusions.

The once-empty training hall twisted, expanding into an endless corridor lined with shifting walls. Shadows danced unnaturally, distorting depth perception. The floor wavered, making it impossible to tell if it was solid or just another trick.

Then—the attacks began.

Blades, spikes, chains—illusions so precise they looked real. Each one aimed to test his reflexes. If he hesitated, his body wouldn't be able to keep up.

Kairo moved.

A sharp metal spear came from the left—he ducked. A spiked chain swung from above—he rolled forward, narrowly avoiding it. The floor beneath him cracked open, revealing an endless pit. Fake. He leaped over it anyway.

Mei wasn't holding back.

His heart pounded. His mind sharpened.

Every movement had to be calculated. Every reaction had to be instant. His instincts had to adapt.

But that wasn't enough.

Just dodging wouldn't help him win a real fight. He needed to counter.

"How do I fight something that isn't real?"

Then it hit him.

"Illusions rely on perception. But my quirk doesn't."

Kairo's body vibrated, sending out a shockwave pulse—not an attack, but a ripple that distorted the air around him. The illusions flickered for a split second.

"There!"

He rushed forward, ignoring the fake attacks and striking directly at Mei's real position.

His fist stopped just short of her face.

The illusion shattered.

Mei blinked, surprised.

Then she laughed.

"Not bad. You figured it out quicker than last time."

Kairo smirked, catching his breath. "I adapt."

Mei patted his shoulder. "Good. Because next time, I'll make sure you can't."

As Kairo entered the classroom later that morning, the air still felt… different.

His match with Todoroki and Kenta had left an impact. Everyone had felt it.

Some, like Bakugo, seemed annoyed—like he had something to prove. Others, like Tokoyami and Iida, analyzed him with newfound caution. Even Todoroki, usually unreadable, gave him a contemplative glance before returning to his usual silence.

"Yo, Kairo!" Kirishima grinned. "That match was insane! You were like—BOOM! And then—" he mimicked an explosion.

Momo nodded. "Your use of shockwaves to disrupt the battlefield was impressive. But…" she hesitated. "You took a lot of risks."

Kairo shrugged. "Calculated risks."

Momo sighed. "You say that, but still…"

Izuku, sitting nearby, had been furiously writing in his notebook. When he looked up, there was something different in his eyes.

"Your quirk… It's not just about creating force, is it?" he muttered.

Kairo raised an eyebrow. "What do you mean?"

Izuku tapped his pen against the page. "From what I observed, you don't just release shockwaves—you manipulate how they interact with the environment. You used vibrations to detect illusions, disrupted Todoroki's ice without outright breaking it, and even redirected projectiles. That's not just raw strength—that's control."

Kairo stared at him.

This kid…

He was way too sharp.

A small smirk formed on his lips. "Guess you'll have to see what else I can do."

Izuku grinned. "I will."

After classes Kairo entered the training hall with his notebook, flipping through pages filled with sketches and calculations. This wasn't just about brute force—it was about control, efficiency, and mastery.

"Speed, strength, reflexes, and defense—I need to optimize all of them. But I won't get everything on the first try. I have to refine, adjust, and push my limits step by step."

He had observed how others fought.

Todoroki controlled temperature zones, limiting movement.

Izuku mastered quick bursts of power for instant acceleration.

Bakugo used explosions for mid-air maneuverability.

Iida relied on engine-assisted bursts for speed.

Each had a method to maximize their strengths.

Kairo needed his own.

"My quirk already enhances my strikes. But what if I could reinforce every part of my body, not just my fists?"

The goal: Create a full-body reinforcement technique using micro-vibrations.

First attempt—Failure.

He tensed his muscles, trying to send small shockwave pulses through his arms and legs. The vibrations were uneven—his left arm felt heavier, his right leg lighter. No balance.

"I need even distribution. Otherwise, I'll just destabilize myself."

Second attempt—Partial Success.

He tried again, this time focusing on his breathing. Inhale. Vibrate the fibers evenly. Exhale. Keep the shockwaves controlled.

This time, his punches had more weight behind them—his strikes carried extra force without extra effort. But there was a problem.

Endurance.

The constant micro-pulses drained stamina fast. His arms felt heavier after just a few minutes. Sustaining this for long battles would be impossible.

"More control. Less waste. I need to find the sweet spot."

"Speed isn't just about moving fast—it's about reacting before the opponent does."

Kairo wanted to shorten his reaction time.

Normal reflexes: The brain sends a signal -> The body moves.

Enhanced reflexes: What if he could skip the delay by stimulating his own nerves?

Test 1: Can I use micro-shockwaves to speed up nerve impulses?

He focused a gentle vibration along his spine, targeting the sensory and motor neurons.

First, he tested it with simple movements.

Snapping his fingers? Faster.

Blinking? Faster.

Clenching his fist? Immediate.

"It works. But that's not enough."

He set up a reaction drill.

A machine launched ten rubber balls at him from different angles. His goal? Dodge, block, or deflect every single one.

The first round—he dodged six, got hit by four.

The second round—seven dodged, three hit.

The third round—eight dodged, two hit.

It was working.

But there was a flaw.

His body moved faster—but if his mind couldn't keep up, it didn't matter. He needed to train his perception speed too.

"My eyes need to process movement as fast as my body reacts."

That's when he remembered—Mei's illusion training.

"Illusions mess with my perception. What if I train under that again, but push my reaction time to the limit?"

A new idea.

He made a mental note to ask Mei for another session—but this time, he wouldn't just dodge.

He'd counter.

Kairo wiped the sweat from his forehead, moving to his next experiment.

"Todoroki's ice walls, Kirishima's hardening, Sero's tape—these all provide defense. I need my own version."

His idea: A thin, constant shockwave layer around his body, repelling attacks.

First attempt—Failure.

He generated a constant outward pulse, trying to keep it stable. Instead, the waves fluctuated—too weak in some areas, too strong in others. Inconsistent.

"I need a way to regulate the output."

He thought back to sound waves.

If a speaker played at one frequency, the sound was clear. But if the frequency kept changing? Distorted noise.

His shockwave barrier was the same—it needed a steady frequency.

Second attempt—Better, but not stable.

He tried again, focusing on rhythm. Instead of a constant pulse, he used small, controlled bursts—like a heartbeat.

When a rubber projectile was fired at him—it slowed down before impact.

Not perfect. But progress.

Kairo's last focus was integrating what he learned from watching his classmates.

Todoroki's control over zones? He needed to work on manipulating air pressure with shockwaves. If he could alter movement zones by making areas heavier or lighter, he could control the battlefield.

Izuku's explosive bursts? Instead of maintaining constant power, he should experiment with shockwave bursts for mobility—short, instant acceleration instead of long-lasting power.

Bakugo's mid-air movement? If he could use shockwaves for redirection, he could fake movements and adjust course mid-air.

Iida's high-speed balance? Running fast wasn't just about speed—it was about stability. He needed to figure out how to keep his balance at max velocity.

By the time he finished, his body was screaming.

His muscles ached. His breath was heavy. His mind was exhausted from constant calculations.

"I didn't perfect anything today."

But he had made progress.

His shockwave reinforcement had started forming.

His reaction time technique had proven effective.

His shockwave barrier had shown promise.

His battlefield control ideas were beginning to take shape.

Kairo collapsed onto the ground, staring at the ceiling.

"This is just the beginning."

His body was tired, but his mind was already racing to the next step.