Morning sunlight poured into the Akari household like liquid gold, bright but gentle, the kind that warmed the skin instead of hurting the eyes. At age ten, Arlan Kurogane had grown into a calm, sharp-eyed boy with a mind far too brilliant for his age.
And unlike most prodigies in history, he wasn't lonely.
Because she was always beside him.
Momo Yaoyorozu.
Today was no different.
As Arlan opened his eyes, he immediately felt warmth pressed against his right side. A familiar softness. A faint scent of lavender. And an arm looped securely around him.
Again.
Arlan exhaled. "Momo… you snuck in."
Her sleepy voice answered, muffled into his shoulder, "Your house security is too easy. You should improve it."
"For a ten-year-old girl, breaking in at 5 a.m. shouldn't be 'easy.'"
She only tightened her hold.
"You weren't waking up," she murmured. "I didn't like that."
There it was again—the possessiveness that had grown stronger every year.
Not toxic.
Not harmful.
Just incredibly, overwhelmingly affectionate.
And impossible to refuse.
Arlan gently patted her head. "I'm awake now."
"Good," she whispered, finally relaxing.
They stayed like that for a while. Soft. Quiet. Warm.
Just two children—yet their bond was deeper than most adults would ever feel.
Momo eventually sat up, brushing her long black hair behind her ear. At ten, she had grown elegant and intelligent beyond her years—her posture perfect, her expressions calm… except when Arlan was involved.
Then she became a different person entirely.
"Arlan," she said, "you promised to show me your new invention today."
Arlan stretched. "I did. And I will."
Her eyes brightened—subtly, but unmistakably.
She loved seeing his genius at work. Admired it. Worshipped it quietly.
And that admiration only made Arlan want to show her more.
The Lab Beneath the House
They moved through the large Akari mansion, still silent in the early morning, until they reached a particular wooden panel in the hallway.
Arlan knocked twice.
A soft chime answered.
The panel slid open silently.
Momo still shivered with excitement every time she saw it.
A hidden elevator.
Built by a ten-year-old.
Arlan stepped inside and Momo followed, standing close—closer than necessary—but Arlan had long accepted it.
With a soft hum, the elevator descended deep underground.
Lights flickered on as the doors opened.
A vast technological sanctuary sprawled before them.
Holographic screens.
Blueprint tables.
Energy reactors.
Instrument racks.
Sound isolation chambers.
Prototype armor stands.
And a central desk filled with glowing music-based devices.
Momo inhaled. "I still can't believe you built all this before age ten."
Arlan shrugged. "I was bored."
She gave him a look that said: Stop pretending you're normal.
"I had help," he added after a moment.
"From who?" she asked.
He pointed at his own head.
"My brain."
She sighed—softly, affectionately—but didn't push further.
Because she already knew the truth:
Arlan Kurogane hid 99% of his capabilities from the world.
Only one person got to see even a fraction of it.
Her.
The New Invention
Arlan walked toward a pedestal covered with a dark cloth.
Momo followed behind, hands clasped neatly… but her eyes full of anticipation like a child about to unwrap a birthday present.
"Is this the new project?" she whispered.
"One of them."
He pulled the cloth away.
Momo gasped.
It was a small, sleek floating speaker-orb, about the size of a grapefruit, marked with glowing blue music sigils. It pulsed softly—alive with rhythmic energy.
"What does it do?" she asked.
Arlan tapped the orb gently.
"It listens."
"To what?"
"To me."
He took a breath—and sang a single note.
Just one.
The orb vibrated.
Sparked with light.
Then burst into a soft, harmonic ripple that washed through the entire room like a warm wave.
Momo's eyes widened. "It amplifies your quirk?"
Arlan smiled. "It harmonizes with me. Makes my singing safer. Stronger. More stable."
He touched the orb again.
"It's the first step toward a full-scale Musical Resonance Network."
Momo blinked. "Meaning…?"
"Meaning someday," he said, eyes gleaming with calm brilliance,
"I'll be able to sing once… and change the entire battlefield."
Momo's breath caught.
Not in fear.
In awe.
"You're incredible," she whispered.
Arlan didn't respond immediately.
He wasn't good at taking praise.
Especially from her.
Momo moved closer—very close—placing a hand over his.
"You really are," she said softly. "You're going to change the world."
Arlan met her eyes.
Warm.
Intelligent.
Devoted.
And fiercely loyal.
"Maybe," he whispered, "but I don't want to change it alone."
Her hand tightened over his.
"You won't," she said. "I'll be there. Always."
A Growing Bond
After testing the orb, Arlan and Momo moved to the central workspace.
She sat beside him—so close their shoulders brushed—and watched him with quiet fascination as he adjusted circuits and tuned harmonic frequencies.
Momo loved watching him work.
She said nothing.
Did nothing.
Just stayed close.
Like she belonged at his side.
Arlan had long accepted it.
Though he never said it aloud…
He liked it.
More than he could admit.
"You're staring again," he murmured without looking up.
"I'm allowed," she said calmly.
He sighed softly—but couldn't hide the tiny smile forming.
This was their routine.
Their peace.
Their childhood.
Together.
And as Arlan worked, his mind moved through fresh calculations, new inventions, new dreams.
He would become a hero.
An inventor.
A performer.
A singer.
He would become more than anything this world had ever seen.
And Momo…
She would be with him through all of it.
She had decided that long ago.
A Morning Experiment Gone… Too Well
"Alright," Arlan said, adjusting the last harmonic stabilizer, "I'm going to try something a little different."
Momo straightened, her posture sharpening in seconds.
Different meant dangerous.
Dangerous meant she would not let him take even one unnecessary risk.
"What kind of different?" she asked, her voice calm but edging toward protective.
"Nothing reckless," Arlan assured. "Just a… higher-frequency resonance test."
"In simpler words," she said, narrowing her eyes.
"I'm going to sing a higher note."
Her expression tightened.
She remembered last time.
He'd broken fifteen glass panels when he was eight.
And she had nearly dragged him away from the microphone by force.
Arlan raised both hands.
"It's safe now—this orb stabilizes the output."
Momo still crossed her arms.
"I'm standing right next to you."
"You always do."
"Closer than usual."
"That's… intimidating."
"That is the point."
Arlan exhaled.
She really was getting more protective each year.
But it wasn't bothersome.
It was—strangely—comforting.
"Fine," he said. "Stand wherever you like."
Momo stepped right beside him.
Right beside.
Their shoulders touching.
He swallowed. "You're close."
"Good."
⸻
The Note
Arlan positioned the orb at chest height.
Its blue glow pulsed softly—synchronizing with his heartbeat.
He inhaled.
Focused.
Let the world fall silent.
Then sang.
Just one note.
A clean, high, pure tone.
Everything changed instantly.
The orb spun, rising slightly into the air.
Harmonic rings spread out from it—gentle, warm, glowing like morning light.
The lab floor vibrated.
Panels lit up.
Energy readings spiked.
Momo's eyes widened—but she didn't move.
The note grew stronger.
Richer.
More powerful.
And then—unexpectedly—
A shockwave burst out.
Not violent.
Not dangerous.
But strong enough to push papers across the lab and make the lights flicker.
Momo reacted first.
Before Arlan could even blink, she grabbed him and pulled him backward into her arms, shielding him with her body.
"Momo—!"
"Arlan, stop!"
He let the note fade instantly.
The orb dimmed.
The vibrations ended.
The lab became silent again.
Momo's arms remained locked tightly around him, her chest pressed against his back.
"…Are you hurt?" she asked.
"No."
"Are you sure?"
"Yes."
"Really?"
"Momo, I'm fine," he said, turning to face her.
Her eyes softened only after confirming he wasn't even scratched.
Then she did something he wasn't prepared for—something she had started doing more often recently.
She gently cupped his cheeks with both hands.
"You're not allowed to get hurt," she whispered.
He blinked.
"That's… not possible. I'm training to be a hero—"
"I don't care," she whispered. "You're not allowed to get hurt."
Her fingers trembled slightly, betraying the fear she never voiced.
And Arlan felt a strange tightness in his chest.
"Momo," he said quietly, "I'm not fragile."
"I know."
She looked down.
"But I care."
⸻
A Quiet Understanding
She lowered her hands slowly, stepping back—but not far. Never far.
Arlan studied the orb, reviewing the energy output.
"The resonance is stronger than expected," he murmured.
Momo crossed her arms. "Then no more high notes today."
He turned. "I need to test—"
"No."
He raised an eyebrow.
She raised both eyebrows.
He sighed.
"Fine. No more high notes."
Her expression softened instantly.
He hesitated, then added:
"Not today."
She accepted that.
Because she trusted that he would listen to her.
Arlan picked up the orb again, letting it settle back onto the pedestal.
"I'll reinforce the stabilizers before the next test," he said.
"I'll help," Momo added.
"You don't need to."
"I want to."
That was the end of the discussion.
⸻
Late Morning — Breakfast at the Mansion
They returned upstairs around 8:30 a.m., where the Akari dining room was already prepared.
Momo sat beside Arlan, as always, much to his mother's quiet amusement.
Hana Akari sipped her tea with a smile.
"Good morning, you two. Testing new inventions again?"
Momo nodded. "Arlan's quirk is developing rapidly. He needs supervision."
Arlan shot her a look. "…Supervision?"
She nodded again. Firmly.
His father, Kenji Kurogane, chuckled. "She's not wrong."
Arlan sighed.
This was his life.
Momo stole a piece of his omelette without breaking eye contact with him.
He blinked. "That was mine."
"It is now."
He opened his mouth—but she fed him the piece she stole.
His mother nearly melted.
"Oh my goodness… how adorable…"
Arlan nearly choked.
Momo remained perfectly calm, patting his back once.
"Eat slowly."
"You're the one who shoved food into—never mind."
She looked satisfied.
⸻
A Sudden Idea
While eating, Arlan's mind buzzed with new possibilities.
Music energy…
Resonance output…
Orb stabilization…
Emotional linkage…
Then—
His eyes widened.
"Ah."
Momo froze mid-bite.
"What did you think of?"
Arlan didn't answer immediately.
He pulled a napkin and began scribbling with a pen.
Momo leaned close, eyes following the rapid sketches—circles, waveforms, arrays, focusing modules.
After thirty seconds, she whispered:
"Arlan… this is…"
"A resonance amplifier."
"No… this is more than that."
He nodded.
"Yes."
A portable device.
Wearable.
Compact.
Energy-reactive.
Something that would strengthen his quirk, stabilize his voice, and channel musical power into precise combat applications.
A Musical Combat Suit.
The first of its kind.
Momo stared at the sketches in awe.
"If you finish this…" she whispered, "you'll be unstoppable."
Arlan corrected her gently.
"We'll be unstoppable."
Her eyes softened.
"No," she whispered. "You will."
"And you'll be right next to me."
She paused.
Then a small, satisfied smile appeared.
"Yes."
⸻
A Promise in the Making
Breakfast ended.
Arlan cleaned the table; Momo helped—though she mainly stayed close to him rather than being useful.
As they walked toward the garden, she tugged his sleeve gently.
"Arlan."
"Hm?"
"When you build that suit…"
He turned to her.
"…Promise me something," she whispered.
"What?"
A long pause.
Then her voice—soft but fierce:
"Promise me you won't use your quirk recklessly.
Promise me you won't put yourself in danger alone.
Promise me you'll trust me enough to let me protect you too."
Arlan blinked.
That wasn't a childish request.
That was a vow.
"Momo…" he murmured.
She looked up, eyes steady.
"Promise me."
He held her gaze.
Calm.
Warm.
Resolute.
"I promise."
Her shoulders loosened, relief washing over her carefully controlled expression.
And then she stepped forward and hugged him.
Not aggressively like when they were toddlers.
But gently.
Softly.
Intimately.
Warm.
"Thank you," she whispered into his shoulder.
Arlan closed his eyes briefly.
"…You're welcome."
The hours drifted by, the way time often did when Arlan became absorbed in creation. Tools clinked softly, monitors hummed, and the faint glow of energy-lines across the lab walls pulsed in a slow rhythm.
Momo sat beside him, quietly reading a research file he'd written—something about harmonic stabilizers and audio-kinetic circuits—though she understood maybe half of it.
But she didn't mind.
She never minded.
Being near him, watching him, simply existing in his orbit made her feel… complete.
She glanced at him out of the corner of her eye.
Even absorbed in calculations, he looked calm. Focused. A little too mature for ten years old—but she liked that. Admired it. Relied on it.
And something inside her softened every time she realized:
He trusted her enough to let her be here.
Most people didn't get this close to him.
Not physically.
Not mentally.
Not emotionally.
Only her.
⸻
A Quiet Conversation
"Arlan," she said softly.
He didn't look up, but his hand paused. "Mm?"
"Do you ever get tired?"
"Tired of what?"
"Everything you're doing." She lifted the notes carefully. "All of this. Studying. Inventing. Designing. Training. You never stop."
Arlan didn't answer immediately.
Instead, he set his tools down gently and leaned back in his chair, exhaling.
A rare moment of stillness.
Finally, he said, "I don't get tired of the work… but sometimes I get tired of the expectations."
Momo blinked. "Expectations?"
"My parents think I'm talented," he said quietly. "The world thinks I'm a genius. Reporters say I'm some kind of miracle child." A soft sigh. "Everyone already expects me to be something great."
She listened, silent and attentive.
"It's a lot," Arlan admitted.
Momo closed the folder and turned toward him fully.
"You don't owe anyone greatness," she said. "Not the reporters. Not society. Not even your family."
He looked at her with a mixture of surprise and something… warmer.
She touched his hand—lightly, gently, but with purpose.
A reassuring warmth.
"You only owe yourself happiness, Arlan," she said firmly. "That's all."
Arlan studied her face.
Steady. Elegant. Mature.
And deeply protective in her own quiet way.
He felt a small, but genuine, breath ease out of his chest.
"…Thanks, Momo."
She nodded, returning to her calm posture. But her eyes lingered on him for a moment longer—soft and full of quiet devotion.
⸻
Testing the New Idea
A few minutes later, Arlan stood up from the workbench, stretching his arms.
"I want to test something."
Momo perked up instantly. "Your quirk?"
"Part of it."
He walked toward a circular platform built into the center of the room. Momo followed, hands clasped neatly behind her back, eyes sharp with curiosity.
Arlan stepped onto the platform.
Then breathed in.
And sang.
A gentle note.
Soft, low, and warm.
The floating resonance orb across the room lit up, humming to life.
Lines of energy formed around him like faint ribbons of light—responding to his tone.
Momo watched, entranced.
His voice wasn't loud.
It wasn't dramatic.
It wasn't flashy.
But it was… beautiful.
Resonant.
Pure.
The type of sound that wrapped around the heart before it reached the ears.
The energy around Arlan pulsed softly, matching the rhythm of his voice. Controlled. Stable. Balanced.
When the last note faded, the lights slowly dimmed.
Momo stepped closer—almost unconsciously. "It's stronger than before."
"Yes," Arlan said, stepping off the platform. "And more precise."
She tilted her head. "You don't look tired."
"That's the point. Previously, holding a resonance field drained my stamina. But now—"
He lifted the orb.
"It helps carry some of the load."
Momo looked at him with subtle pride. "You're closer to mastering it."
"Closer," he agreed, "but not done."
She smiled slightly. "You'll finish it. I know you will."
⸻
Lunch Break… in Their Own World
After more testing, Arlan's mother called them up for lunch.
The dining table at the Kurogane household was large and elegant, but the atmosphere was peaceful. His parents adored Momo and treated her like family. She sat next to Arlan, as always.
His mother placed warm food on the table. "You two have been working since morning. Eat well."
"Yes, Auntie," Momo answered politely.
Arlan's father chuckled. "Our little genius is rubbing off on her."
Momo glanced at Arlan.
He didn't deny it.
Instead, under the table, he nudged her foot lightly.
A silent acknowledgment.
She smiled faintly.
⸻
A Moment Beneath the Cherry Tree
After lunch, Arlan and Momo moved to the back garden—quiet, spacious, lined with gentle greenery. A single cherry blossom tree stood near the center, still full of late-season petals.
They sat beneath it, side by side.
No tools.
No calculations.
No inventions.
Just peace.
Momo leaned back against the trunk. "It's beautiful today."
"Mm," Arlan hummed.
She glanced at him. He was watching the sunlight through the branches—calm, thoughtful, almost serene.
"You know…" she began softly, "sometimes I think you carry too much alone."
"…Maybe."
"You always look ahead. Always planning. Always trying to improve. But you never stop and think about yourself."
Arlan looked at her. "And you?"
"I think about you all the time."
He blinked slowly.
Her voice was calm, matter-of-fact, but warm in a way that always melted his emotional guard.
"You don't have to do everything alone, Arlan," she said. "You have me."
"I know," he whispered.
For a long moment, they sat quietly, the wind scattering pink petals around them.
Momo shifted slightly closer until their shoulders touched.
Just barely.
Just enough.
Arlan didn't move away.
⸻
A Soft Decision
"Arlan," she said suddenly.
"Hm?"
"When we grow up… when we enter U.A.… when you become the hero you want to be…"
She breathed in, steadying herself.
"…I want to be beside you."
Arlan turned to her.
Her eyes were steady.
Her voice gentle.
Her expression unshakable.
Not dramatic.
Not forceful.
Not intense.
Just certain.
"Momo…"
She continued, almost whispering:
"You don't need to say anything now. But I want you to know… I'm not going anywhere."
The words were soft, but they wrapped around his chest like warm music.
He didn't know what his future looked like.
He didn't know how far his power would grow.
He didn't know how the world would react to a genius with a dangerous voice.
But one thing felt solid.
One thing he didn't doubt.
"Momo," he said quietly, "I… like that you're here."
Her breath hitched.
Just a little.
Then she smiled—soft, beautiful, glowing like a quiet sunrise.
"And I like being here," she replied.
⸻
The Evening Glow
They stayed under the cherry tree until the sun began to set.
Talking.
Laughing softly.
Sharing small, peaceful moments.
Not rushed.
Not dramatic.
Nothing explosive.
Just two hearts growing closer in a quiet, natural way.
Momo leaned her head against his shoulder.
Arlan let her.
And the world felt simple.