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English
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Part 1 of BNHA story
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Published:
2025-10-28
Updated:
2026-07-23
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399,508
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132/?
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The Sea Within Her: Hydrachain

Summary:

Aizawa's POV

The stench of salt and decay clung to the air, heavy enough to choke on. My boots sank into mud and debris as I moved through what used to be Hoshima Town. The streets were drowned, cars half submerged, and windows shattered.

“What the hell happened here?” I muttered.

Beside me, Best Jeanist adjusted his collar, “No reports of storms, no seismic activity. This wasn’t nature.”

Endeavor stepped ahead. “Hoshima was known for its still waters, the sea so calm it mirrored the stars. Now it’s a graveyard.” His voice was low, edged with restrained anger.

Bodies floated between buildings, faces pale and still. The smell of brine and rot pressed into my lungs. Three thousand lives gone without warning.

Jeanist’s voice cracked slightly. “An entire town erased overnight.”

I kept walking, scanning through the haze, when Endeavor halted near a collapsed carriage. He was speaking quietly.

I approached. “Endeavor, what—”

Then I saw her.

A small girl crouched inside the rusted carriage, drenched, shaking, eyes glassy with fear. Her tiny fingers clutched her knees, knuckles white.

My heart sank. “A… child survived?”

Notes:

Boku no Hero Academia belongs to the owner Kohei Horikoshi. The only thing that belongs to me are the original characters that aren't from the anime, I might have added a bit more backstory on some canon characters due to my original characters appearance. The only ones that truly belongs to me are my ocs quirks, pasts, and lore

⚠️THERE IS GONNA BE 50+ CHAPTERS⚠️

And the only thing that I ask you readers to be is to be patient I can't publish every day. It takes some time so please be patient.

Also, it'll have all of the the original BNHA arc and some will be original. But some canon arcs in the BNHA will change up a bit because of the appearance of my OC's

This is a rewritten story of the old BNHA story, since the other one was more complex and complicated. Also this will be written in First Person comparing to my other fanfic stories in Third Person. Another thing, in the relationships section, please know that & and / are not the same thing, & is a platonic/familiar relationship while the / is a romantic relationship so before you come at me with the unusual tags, please read the notes first

Chapter 1: How It All Began

Chapter Text

Aizawa's POV

“Kid,” Endeavor’s voice rumbled, heavy and impatient. “How did you survive?”

She only shook, refusing to meet his gaze.

Best Jeanist crouched beside me, his tone measured. “Five, maybe six years old. No older than ten.”

Endeavor exhaled sharply, steam curling from his shoulders. “Get out of there. I’m not dragging you out.”

I shot him a glare. “Back off. She’s terrified, not stubborn.”

He clicked his tongue and ignored me. One broad hand reached in, yanking her out before I could stop him. Jeanist’s voice snapped, “Endeavor—!”

Then came the sound — not a scream, but a raw, broken wail that sliced through the silence. It made my teeth clench. She flailed, striking his chest with tiny fists. “Let me go! I don’t wanna go!”

“Endeavor, put her down!” I barked.

He glared back, his flame dimming against the drizzle. “What’s she so afraid of? The flood’s gone. We’re trying to help—”

“You’re not heroes! You didn’t save them!”

Endeavor froze. The rain hissed against his fire.

When her knees buckled, I moved on instinct, catching her before she fell face-first into the mud. She was light — too light.

Endeavor turned away, muttering, “Ungrateful brat. Send her to an orphanage.”

Jeanist’s jaw tightened. “First stop’s a hospital.”

I adjusted my hold, feeling her cold skin against my gloves. “Jeanist,” I murmured.

He met my eyes.

“Look at her wrists.”

The marks were faint but deliberate — thin, circular bruises, almost symmetrical.

Jeanist’s voice lowered. “From restraints?”

I nodded once, my stomach twisting. “Or thin metal bands.”

And for the first time that day, the silence felt heavier than the flood itself.

The ride to the hospital was suffocatingly quiet. The hum of the engine was the only thing keeping me grounded. Every bump in the road made me tense, careful not to wake the girl resting against my chest. Her body was cold, her breathing shallow, and I could feel her pulse flutter weakly against my arm.

Something brushed against my fingers—soft strands of tangled violet hair. I exhaled slowly, trying to free my hand without pulling too hard. No use. My fingers were stuck in the mess.

Jeanist glanced at me through the rearview mirror. “You okay? You look like a mannequin.”

“Can’t move,” I muttered. “She’ll cry again if I do. And my fingers are… trapped in this nest.”

He huffed a short laugh—nervous, tired. “That’s a first. Eraserhead, taken down by hair.”

“Don’t start,” I said, voice flat.

When we arrived, the hospital lights cut through the fog outside—too bright, too clean. It smelled of antiseptic and stale air. I stepped out carefully, still holding the girl. Her weight was nothing, but every part of me felt heavy.

A nurse hurried toward us, her eyes wide. “Sir, please—bring her this way!”

“Careful,” I said quietly, lowering my arms inch by inch. My hair fell over my face as I tried to untangle my hand from hers. “She’s… sensitive to touch.”

The nurse reached out, but I couldn’t bring myself to let go. Not yet. Finally, I shifted my grip, sliding her into the nurse’s arms with the precision of disarming a trap. My hand lingered a moment too long before I forced it back.

Jeanist spoke with the staff, his voice calm and polished. Endeavor had already stormed off hours ago—typical. I stayed behind. My body refused to leave the sterile hallway.

Hours blurred. I sat on a cold bench, watching the rain trace down the window like veins. Every time the door opened, I half-expected someone to say she didn’t make it. Instead, nurses passed by with polite nods, too busy to notice the underground hero sinking into the wall.

By sunset, I gave up pretending I’d leave. I pulled out my phone, thumb hovering over a contact. Then another. Midnight. Present Mic. Nezu.

I sighed. “Looks like I’ll need some help.”

The hospital lights buzzed above me, a low hum that refused to die. My coffee had gone cold hours ago, but I didn’t care. By the time the clock hit midnight, footsteps echoed down the hall. Midnight, Mic, and Nezu appeared together.

Midnight’s voice broke the stillness first. “Hey, how’s the little girl?” Her tone was softer than usual, stripped of her usual teasing edge.

Jeanist turned to face her and Nezu, who perched on her shoulder like a commander assessing a battlefield. “Doctors say she’s quirkless,” Jeanist said, brushing his hand through his perfectly arranged hair. “But… she’s severely traumatized.”

My eyes drifted past them, catching a faint shimmer on the floor—water, threading its way out from under a door across the hall. The sound of faint dripping cut through the sterile air.

I frowned. “Hey,” I called to a nearby doctor, “I think someone clogged your bathroom.”

The doctor blinked, puzzled. “That’s not possible.”

Nezu climbed up onto my shoulder, his small claws light but sharp against the fabric of my capture scarf. “And why’s that?” he asked, voice chipper but eyes narrowed.

The doctor’s brow furrowed. “Because that’s not the bathroom. It’s one of the patient rooms.”

A chill crawled down my spine. Something wasn’t right. The quiet was too heavy. Too forced.

“Everyone out,” I barked, louder now. “Evacuate, now!

The door exploded open before the words even finished leaving my mouth. A rush of cold water slammed into the hallway, swallowing the light, the sound, the air. It was freezing—sharp as needles against my skin.

Mic staggered back, shielding his face. “What the hell—where’s all this water coming from!?”

A doctor burst through the chaos, soaked to the bone, shouting above the noise. “That’s— that’s the room of the girl you brought in!”

The hallway reeked of disinfectant and salt. My scarf was heavy, dripping. I stared at the flood, every instinct screaming that whatever happened in that room… it wasn’t natural.

The hallway tiles slick beneath my boots, reflections of the emergency lights distorted in the spreading water. My chest tightened. The door to the patient’s room had swung open on its own. I pushed forward, voice taut.

She wasn’t there.

My stomach dropped, instincts screaming. Not quirkless. Water. Dangerous. Uncontrolled.

“Midnight, Mic, Jeanist—evacuate the patients, now!” I barked, voice low and clipped. “Nezu, coordinate exits, calm the staff.”

Footsteps and murmurs blurred as the pros dispersed, leaving me alone with the cold metallic tang of the hospital and the faint scent of damp antiseptic. A nurse stepped up, shaking. “The cameras… sir, the girl just vanished.”

Jeanist led me to the monitors. The footage replayed: the girl asleep in the room, then… nothing. My gaze snapped upward, catching movement on the rooftop. A flash of violet hair, pale and trembling.

Another quirk.

I vaulted the railing instinctively, landing softly behind her. She crumbled, knees buckling, shaking violently. My scarf uncoiled silently. “Hey… come with me,” I murmured, careful, quiet, trying not to startle her. “We need to leave the rooftop.”

Her lips quivered. “I don’t want to… go back. Not the white room…”

I froze for a heartbeat, processing the words. Confusion. Guilt. Fear. Her tone was brittle, desperate.

I inched closer, arms ready, voice steady but firm. “It’s not safe here. You’ll hurt yourself.”

She recoiled, stepping back with each movement.

And then her knees gave out. Gravity pulled her, her small frame teetering over the edge. My scarf shot out, coils wrapping around her instantly. She dangled, limp, the wind whipping at her soaked clothes.

Screams erupted below. Bystanders pointed, panicked, some stepping back as the unconscious girl swayed in the capture scarf. My chest tightened, jaw set. One wrong move, and this could’ve been a disaster.

I carefully carried her down the hospital steps, the wet asphalt slick beneath my boots. Her small body trembled against me; ragged breaths, faint whimpers, the taste of iron from a cut on her lip lingering in the air. I grabbed a nearby blanket, wrapping her tightly, feeling her warmth against the chill of the night.

The other pros converged silently, eyes sharp.

“She needs immediate medical attention and psychological evaluation,” I said, voice low, firm.

Nezu’s tiny hands patted her head gently, his whiskers twitching. “She’s suffered so much.”

I nodded, jaw tight. “Her quirks are unstable… and she’s deeply traumatized.”

Jeanist exhaled, the tension in his shoulders visible. “We can’t just send her to an orphanage, either.”

I looked down at her exhausted face. Her violet hair stuck to her pale forehead, lips quivering. “No,” I said quietly. “She’s too dangerous for that. She needs specialized care… protection.”

The rumble of flames announced Endeavor’s arrival. He strode up, eyes blazing. “Then I’ll take her.”

I instinctively stepped back, pulling her closer. “Absolutely not. You’re the last person who should be responsible for a child’s well-being.”

Edgeshot’s calm voice cut through the tension. “What about you? With your quirk, it could help.”

Wait. Me?

Mic nodded, voice high and anxious. “You’ve been attached to her the entire day. You’ve got the connection.”

Midnight leaned closer, a rare softness in her expression. “And it’ll be adorable. You caring for a little girl.”

I groaned, rolling my eyes. “I’m an underground hero. Not a babysitter.”

Nezu’s small form tilted, observing quietly. “Babysitter or not… she seems to like you.”

I glanced down. Her tiny left hand clutched my scarf tightly, pale fingers curling instinctively. A sharp exhale escaped me. “What did I get myself into…”

Mic chuckled, the sound high-pitched in the night. “I think that’s a yes.”

Midnight tilted her head, mischief in her eyes. “How about thinking of becoming a teacher at U.A., too?”

I stiffened, voice sharp. “Okay, woah. One thing at a time.”

Even as I said it, the weight of her in my arms, her trust, and the storm of potential danger she carried pressed into me like nothing I’d ever faced. This wasn’t just a rescue. This… this would change everything.

Jeanist drove silently, the hum of the engine and the tires against wet asphalt filling the space between us. I kept her wrapped tightly in a blanket, her small body curled against mine, breaths shallow and uneven. My voice was a whisper, low and steady, “We still don’t know her name.”

Jeanist glanced at me, tone calm but serious. “When she wakes, that should be the first thing you ask.”

Silence fell again. The car smelled faintly of leather and rain. I hesitated, then muttered quietly, almost to myself, “She can’t be known… not by the Hero Commission. They’d weaponize her.”

Jeanist’s eyes darkened. “I agree. She’ll stay hidden… under your care.”

The city lights blurred past, then the familiar streets of my neighborhood came into view. I exhaled sharply. “Thanks for the ride.”

“Careful,” Jeanist said. “Don’t wake her.”

Even walking to my apartment, every step was deliberate. She stirred slightly in the blanket, and I froze, heart thumping. A faint smell of rain and asphalt clung to us both.

Inside, the door creaked, and a small cat padded toward me, purring. Its fur brushed my legs, a warm, grounding presence. I gently laid her on the couch, the blanket still cocooning her. My hand drifted toward her messy violet hair, brushing lightly against the soft strands. I jerked it away, reminding myself sharply: I’m an underground hero, not a babysitter.

It was near midnight when her eyes snapped open, wide and frantic. She stared around, small chest heaving, only to notice the cat leaping onto her lap. Hesitant, she reached out, letting it nuzzle against her.

I stayed in the shadows, finally stepping forward, voice low, measured. “Don’t freak out. You’re safe. You’re at my apartment.”

Her eyes widened with recognition. Voice barely above a whisper, trembling, she asked, “You… you’re…?”

I knelt beside the couch, careful not to startle her, keeping my tone soft but firm. “I’m Shota Aizawa… underground hero. Name’s Eraserhead.”

I hesitated, unsure how to ask what mattered most. “What’s… your name?”

She grew silent, body tense, staring at the ceiling, processing. I rose, giving her space, preparing to leave her to her thoughts.

A fragile, barely audible word broke the silence. “Mizuki.”

I froze, letting the name settle between us. Somehow, in that single word, the night became heavier — yet, for the first time since the chaos, I felt the smallest measure of clarity.