Morning sunlight spread across the Kurogane estate like gentle golden paint, lighting the polished wooden floorboards and warming the air. Arlan Kurogane—now three years old—sat on his bed with his tiny legs dangling over the edge, humming softly to himself.
But this time, the humming wasn't just humming.
A faint musical aura shimmered around him.
The sound of a gentle flute echoed behind his voice, even though there was no flute anywhere in the room. A soft, warm glow shimmered from his chest with each note.
His quirk was waking.
Fully.
Arlan paused, breath steady, eyes focused.
"So this is… the beginning," he whispered.
The melody faded instantly.
Quirk activation at age three was normal.
But using it?
Control?
Clarity?
Most three-year-olds could barely tie shoelaces.
Arlan could feel sound bending under his command.
A Genius's Morning
Hana Kurogane entered the room quietly, smiling at the sight of her son.
"Good morning, Arlan. Already awake?"
Arlan nodded and hopped down from the bed with surprising coordination. His mother noticed instantly.
"You're more stable today," she said warmly. "Growing so fast."
Growing fast wasn't the right term.
Growing efficiently was more accurate.
Arlan's body was slowly catching up to his intellect. His balance had improved. His grip was firmer. His words were clearer. His mind was always racing, always analyzing.
As Hana lifted him into her arms, he murmured:
"Mama, I want to try singing again later."
Hana blinked. "Singing? You're practicing for something?"
Arlan nodded. "I want to be good at it."
His mother kissed his forehead with pride. "Of course. We'll practice today."
She didn't know the full truth.
Singing wasn't just a hobby.
It was power.
Momo Arrives—Like a Missile
The moment they entered the living room, the doorbell rang.
Ding-dong!
Hana chuckled. "Ah. That must be Momo-chan. She's early today."
Early…
For the seventh day in a row.
Arlan braced himself.
The door opened.
"Momo-chan! Good morning—"
Momo Yaoyorozu, now three, marched into the house with the determination of a war general. She spotted Arlan instantly.
Her face lit up like a firework.
"Arlan!!"
She didn't walk.
She launched.
Her tiny arms wrapped around him before he could even say hello, squeezing him with the strength of a toddler possessed by affection.
"M-Momo—air—" Arlan choked.
Hana giggled. "She really loves you."
Momo looked up at Arlan with bright, slightly obsessive eyes.
"My Arlan," she declared proudly.
Hana covered her mouth to hide her laugh. Mrs. Yaoyorozu sighed behind her daughter.
"Momo, dear, you can't claim people."
"Yes," Momo said firmly, hugging Arlan tighter.
Arlan mentally accepted his fate.
Playtime… or Momo-Time
Momo dragged Arlan by the hand to the playroom.
Dragged.
She wasn't even subtle about it.
"Sit," she ordered.
Arlan sat.
Momo sat right beside him—practically on him—then placed a stack of picture books on his lap.
Arlan raised an eyebrow. "Read?"
Momo nodded. "Read to Momo."
Her voice was soft and sweet, but her eyes said:
"If you don't, I will riot."
Arlan opened the first book.
But Momo wasn't looking at the pages.
She was looking at him.
Again.
"What?" Arlan asked.
Momo leaned her forehead against his shoulder.
"Arlan voice… pretty."
His cheeks turned pink.
"Momo… I'm just reading."
She shook her head.
"Pretty."
Her admiration was warm but intense. Too intense. Three-year-olds weren't supposed to look at anyone like that.
But Momo wasn't normal.
She had already decided—deep inside—that Arlan was hers.
And she had no intention of letting anyone else near him.
A Strange Reaction
As Arlan turned the page, he hummed absently—just a light melody under his breath.
And something happened.
The room shimmered.
A faint, soft echo of piano notes joined his voice.
Momo froze.
Her eyes widened in awe.
"Again," she whispered.
Arlan blinked. "What?"
"Again," she repeated, scooting closer.
He hummed again.
The glow returned—brighter this time, warm like sunlight breaking through clouds.
Momo's hands flew to her chest.
"Arlan… magic."
He stopped humming.
And the music disappeared instantly.
Momo immediately reached forward and grabbed both his cheeks.
"AGAIN."
Arlan panicked. "Momo—w-wait—"
"AGAIN!"
"Momo! I need air!"
She stopped only because he squirmed out of her hold.
Her eyes were sparkling with something between excitement and obsession.
She now understood:
Arlan had a quirk.
A powerful one.
And she wanted to hear it again…
And again…
And again.
The Family Realizes Something Is Up
Hana peeked into the room.
"Kids? Everything okay—oh!"
She froze.
Arlan was glowing faintly.
Momo was staring at him like he was a divine artifact.
Mrs. Yaoyorozu's eyes widened. "Is that… his quirk?"
Arlan cleared his throat. "Um… maybe?"
Momo pointed at him proudly.
"Arlan sings. And music comes out!"
Mrs. Yaoyorozu clasped her hands. "How beautiful…"
Momo nodded vigorously. "Pretty. My Arlan is pretty."
Arlan covered his face.
Why was she like this?
Hana knelt beside him. "Arlan, sweetheart, does it hurt? Does the music feel strange?"
He shook his head. "No. It feels… warm."
"Warm?" she repeated.
Arlan nodded.
"Like the music wants to move."
The room went silent.
Mrs. Yaoyorozu whispered, "A quirk with emotional resonance…"
Hana smiled proudly. "Our boy is growing."
Momo hugged Arlan's side.
"My boy."
"Momo!" Mrs. Yaoyorozu scolded.
"No," Momo said simply.
Arlan sighed.
This was his life now.
A True Breakthrough
Later that afternoon, Arlan sat at the small piano set in the living room. He pressed a single key.
A C note.
Soft, gentle.
He hummed.
The note grew louder.
Not because he pressed harder—
Because the quirk amplified it.
A soft breeze brushed the curtains.
The room vibrated faintly.
The air shimmered.
He stopped humming.
Everything went silent.
His quirk had just amplified a musical instrument.
That was new.
He pressed the key again.
Hum.
The note swelled like a blooming flower.
Momo gasped. "Arlan… hero."
Arlan blinked. "Hero?"
She nodded.
"Arlan… sing. Save."
Her simple words hit him harder than he expected.
Hero.
Could he be one?
Would this quirk… this life… let him?
He gently touched the piano.
And he knew.
Yes.
He could.
The sun was beginning its lazy descent by the time the Kurogane mansion settled into its soft evening rhythm. Warm light filled the living room as little Arlan sat cross-legged on the floor, in front of a miniature whiteboard his father had brought out.
Shun Kurogane—normally a calm, composed businessman—was practically trembling with excitement.
"So!" he said, kneeling down. "My son awakened his quirk today!"
Arlan blinked. "Dad, why do you look more excited than me?"
Hana laughed from the couch. "Because your father thinks his son is the second coming of All Might mixed with Beethoven."
Momo, who sat glued to Arlan's left side, added proudly:
"He is."
Shun pointed a marker at her. "Exactly! The young lady understands."
Arlan stared at his father.
"I just hummed a little…"
"A little?" Shun repeated dramatically. "Arlan, your humming made the wall vibrate!"
Momo nodded. "And made Momo's heart vibrate."
"Momo," her mother whispered in embarrassment.
"No," Momo said flatly, leaning into Arlan again.
Arlan sighed.
This girl had more cling than industrial-strength glue.
Arlan's First 'Experiment'
Shun uncapped the marker and drew a crude stick figure with musical notes around it.
"This represents you."
"…Dad, why am I bald?"
"Focus, son!" Shun cleared his throat. "Your quirk reacts to sound. Specifically: singing or humming."
Arlan nodded slowly.
"So it's an emission-based sonic quirk. But emotional? Maybe environment-linked too…"
Everyone stared.
Shun blinked. "…you're three."
"Age is irrelevant," Arlan replied with a straight face. "Input and output evaluation is simple."
Momo tugged Arlan's sleeve. "Arlan… say big words again."
He smiled gently at her. "Later."
Momo nodded and snuggled closer.
Mrs. Yaoyorozu watched with soft resignation. "She really has no boundaries… I'm sorry."
Hana waved a hand. "It's fine. Arlan needs a friend."
Momo's eyes sharpened instantly.
"Not friend," she corrected.
Everyone froze.
"What do you mean, sweetheart?" Hana asked.
Momo pressed her cheek against Arlan's shoulder.
"Arlan is Momo's."
Arlan internally screamed.
Shun choked on air. "Ahahaha… children say the funniest things…"
Momo narrowed her eyes protectively at the room.
"Mine."
Mrs. Yaoyorozu facepalmed.
Arlan wondered whether this would get worse with age.
Spoiler: it would.
Testing the Quirk — Toddler Edition
"Okay!" Shun clapped loudly. "Arlan, try humming again!"
"No," Momo said immediately.
Everyone looked at her.
"Why?" Hana asked gently.
Momo puffed her cheeks. "Only Momo listens first."
Arlan blinked. "You want… a private concert?"
She nodded.
Shun whispered, "…I respect the confidence."
Mrs. Yaoyorozu rubbed her temples.
Hana smiled warmly. "Arlan, sweetheart, sing for her."
Arlan sighed but nodded. "Okay."
Momo sat up perfectly straight, hands in her lap, eyes shining like she was watching the world's most precious performance.
Arlan inhaled and hummed a simple, gentle tune.
Soft. Calm. Peaceful.
The air shimmered.
A warm golden light formed tiny particles around him, like drifting sparks during a festival. A soft violin harmony played behind his voice, even though no instrument existed.
Momo clasped both hands over her mouth.
"Pretty… so pretty…"
When he finished, she didn't breathe for a second.
Then—
She tackled him into a hug.
"My Arlan sings for Momo only!"
Arlan groaned. "Air… Momo… air…"
Hana quickly helped peel her off him.
Mrs. Yaoyorozu apologized nonstop. "I swear, I don't know where she gets this from—"
"Her father," Hana deadpanned.
Mrs. Yaoyorozu hesitated.
"…fair."
Unexpected Consequence
As Arlan sat back up, he noticed something strange.
His body felt lighter.
Stronger.
Sharper.
It wasn't just the music around him.
It was inside him.
He looked at his tiny hands.
"I feel…"
Everyone leaned forward.
"Different," he finished.
Hana perked up. "Different how?"
Arlan tapped his chest. "Warm. Like… the music is sitting here."
Shun scribbled rapidly on the whiteboard.
"MUSICAL ENERGY RESIDUE — INTERNAL STORAGE?!??"
Arlan winced. "Dad, calm—"
"That means your quirk has amplification, projection, AND internal enhancement!" Shun declared proudly. "Do you know what this means?!"
Arlan nodded calmly. "That I am highly marketable?"
Hana choked on her tea.
Shun dropped the marker, stunned.
"…yes. Exactly."
Momo nodded firmly. "Arlan is the best."
Arlan looked at her.
"Why do you believe in me so much?"
Momo didn't hesitate.
"Because I love Arlan."
Every adult in the room malfunctioned simultaneously.
Arlan's face turned bright red.
"M-Momo— we're three—"
"So?" she asked innocently, tilting her head.
He had no answer.
A Toddler "Battle" Occurs
Later that evening, Mrs. Yaoyorozu and Momo prepared to leave.
But at the front door, something unexpected happened.
Momo refused.
She planted her feet and hugged Arlan tightly.
"No."
"Momo-chan," her mother sighed, "We have to go—"
"No!" she repeated loudly. "Not leave Arlan!"
"Momo," Arlan said gently, "You'll see me tomorrow."
She shook her head fiercely. "No. Stay."
Arlan blinked.
Then—
He hummed a soft melody.
A tender, peaceful tune.
Warm. Gentle. Soothing.
The air glowed around them.
Momo's tiny body relaxed instantly. Her grip loosened. Her eyes softened.
Arlan whispered, "I promise. Tomorrow."
Momo looked up at him.
"…Promise?"
"Promise," he said with a small smile.
She finally stepped back—only to hold his hand again for one last second.
"Mine," she whispered quietly, just for him.
Mrs. Yaoyorozu carried her out.
Arlan stood there, frozen.
Hana watched him with a teasing smile.
"You two are adorable."
Shun added, "That girl is going to marry you one day."
Arlan panicked. "WHAT?!?"
Hana laughed. "We're joking… mostly."
Arlan covered his face.
He wasn't ready for this.
Not at three years old.
A Spark Begins to Form
That night, Arlan lay in bed, staring at the ceiling.
He thought about his quirk…
About Momo…
About the life he was now shaping in this world.
He hummed again softly.
A faint breeze stirred.
A single glowing musical note floated above his hand.
Arlan's eyes widened.
He smiled slightly.
"So this is just the beginning…"
Tomorrow, he decided, he would try something new.
Something only a genius—and a reincarnated one at that—would think of.
He would begin:
His first invention.
At age three.
Night wrapped softly around the Kurogane household, and the moonlight slipped through Arlan's curtains in pale silver lines. The world was quiet—perfectly quiet.
And that was exactly what Arlan needed.
He sat up in his little bed, his tiny legs dangling off the edge. Even as a toddler, his posture looked strangely composed—almost dignified. His mind was whirring with ideas.
"An internal enhancement system… a melody interface… a resonance amplifier…"
He whispered each idea like it was a treasure he was polishing.
At age three, normal children were learning shapes.
Arlan Kurogane was designing early-stage support equipment.
He slid off the bed, grabbed a thick crayon, and walked to his small desk. At this hour, his parents always let him draw quietly. They had no idea half of his "drawings" were actually formulas.
He pulled out a sheet of paper and began sketching.
Circles. Lines. Arrows. Quick scribbles.
His tiny hand wasn't fully steady yet, but his mind was sharp enough to know what he wanted.
"A portable resonance conductor," he muttered.
"Something to stabilize my quirk when singing… to help me balance the power output…"
He tapped the crayon on the table.
"It has to be small enough for a child, durable, responsive—"
He paused.
Then grinned.
"What if I use… toys?"
His eyes sparkled.
A genius solution.
If adults wouldn't let him handle actual materials, he would use what he could use.
His gaze drifted to a toy microphone sitting on a shelf.
Pink. Plastic. Cheap.
But shaped perfectly.
He toddled over, grabbed it, and placed it on the desk.
"Let's see…"
He removed the plastic back panel.
Inside, there was a small squeaker, two thin wires, and a tiny sound chip.
Arlan stared.
Useless.
Pathetically useless.
But the shape…
The hollow interior…
The tiny circuitry…
He didn't need it to be real support gear.
He just needed a prototype.
He hummed lightly as he worked—half for focus, half for testing.
At the soft hum, the air around him shimmered faintly.
"Good," he whispered. "The output reacts well in enclosed space."
He placed the toy microphone in front of his lips.
This is it.
His first "device."
Not truly functional…
But symbolic.
He hummed again.
The toy vibrated in his hands.
A small ripple of soft light pulsed from it—like a heartbeat.
Arlan froze.
"…Did I just…?"
He hummed again.
Another pulse.
A visible one.
The toy wasn't amplifying sound.
It was simply responding to the quirk's natural resonance.
But to his brilliant mind—
This was a miracle.
"I created my first feedback loop…" he whispered, stunned.
He laughed softly.
A child's giggle, mixed with an adult's victory.
But his moment of triumph didn't last.
Because someone had been watching.
From outside his door.
The doorknob turned slightly.
Arlan's body stiffened.
Then—
creak…
The door opened, and a tiny head poked in.
Long dark hair.
Wide curious eyes.
"Momo?"
She stepped inside in her pajamas, hugging a stuffed bunny.
"Arlan…"
He blinked. "Why are you here?! It's past bedtime!"
She waddled forward on her toddler feet. "Arlan didn't say good night."
"What— you literally left hours ago!"
She shook her head. "Didn't hear it."
"That's not how bedtime works—"
But she was already climbing onto his lap.
He panicked.
"Momo—Momo—careful, the prototype—!"
She stared down at the toy microphone.
"What is this?"
"A… project."
"A toy," she corrected confidently.
"No, it's—"
"A toy."
He sighed.
Fine. Let the three-year-old believe it was a toy.
Momo looked up at him again.
Then leaned her forehead against his chest.
"Why did you sing tonight without Momo?"
Arlan froze.
Her voice wasn't angry.
It wasn't harsh.
It was…
Hurt.
"Momo thinks Arlan forget Momo."
Arlan's soul cracked.
"I didn't forget you," he said softly.
"Promise?"
"I promise."
She looked up at him.
"Pinkie promise?"
And because toddlers are terrifyingly serious—
He did it.
Their tiny pinkies wrapped together.
She smiled instantly, as if the world had been fixed.
Then her eyes wandered to the toy again.
"Arlan is… awesome," she whispered.
His face warmed. "Thanks, Momo."
"No." She shook her head.
"More awesome than other boys."
"…Momo, we're three."
"I know," she said proudly.
She reached up and pressed her forehead to his.
"Arlan belongs with Momo."
His breathing hitched.
"M-Momo—"
She didn't give him time to respond.
She hugged him tightly—again—and held on like she planned to stay the entire night.
And she would have…
If not for:
"MOMO YAoyorozu!!!"
Mrs. Yaoyorozu crashed into the room, horrified.
Momo didn't move.
Still clinging.
Still holding on.
"Just… five… more… minutes…" Momo mumbled sleepily.
"No, young lady! You cannot sneak into their home at night!"
"She teleported?" Shun asked from the hall in disbelief.
"No," Mrs. Yaoyorozu groaned. "She scaled the garden wall."
Hana gasped. "At age three?!"
Momo nodded proudly. "To see Arlan."
Mrs. Yaoyorozu scooped her up with the strength of a mother who'd suffered enough that day.
"Good night, Arlan," Momo muttered, half-asleep.
"Good night," he whispered.
"Mine…"
"Momo!"
The door slammed behind them as they left.
Arlan just sat there in silence.
Shun scratched his head. "Son… you're in trouble."
Hana smiled sympathetically. "In the good way, though."
Arlan collapsed backwards onto his bed.
His quirk was awakening.
His mind was flourishing.
His inventions were beginning.
And Momo Yaoyorozu…
Was becoming a storm he couldn't outrun.
A Quiet Resolution
After his parents left, Arlan stared at the glowing toy microphone on the table.
His future felt huge.
Bright.
Terrifying.
Exciting.
He closed his tiny fingers around the toy.
"Tomorrow… I'll test a stronger note."
He smiled slightly.
"And maybe hide this from Momo."
Because if she found out he was training alone…
She would probably break into his house again.
He lay back on his pillow, exhausted.
The moonlight washed over him gently.
Arlan whispered to the ceiling:
"Watch me… I'll become the greatest hero, inventor, and performer this world has ever seen."
His eyelids grew heavy.
"And… I guess Momo will be there too…"
He fell asleep before realizing he was smiling.