The Heroine is My Stepsister, and I'm her Final Boss - Chapter 154 - 155: Down Bad.

His body wasn’t just crumbling—it was betraying him. A mutiny of nerves and marrow. Flesh that had once moved like lightning now stuttered under its own weight, rib by rib, breath by breath. His bones no longer bent with force—they cracked under it.

Atlas dropped to one knee, not in reverence but in collapse.

A white-hot jolt lanced through his chest, sharp enough to blind him for a heartbeat. Then another.

Each breath felt like drawing razors through his lungs. His ribs ached like they’d been kicked in by a god, each inhale a warning, each exhale a scream. His skin burned with fever, but it wasn’t heat—it was pressure. Something beneath the surface pressing outward, testing the seams.

And then—

[@#$$## Heart is reacting]

His heart didn’t beat. It thrummed, a caged beast behind his sternum, slamming against the bars of his chest like it wanted out. Not a rhythm, not a pulse—something wild, something old.

Atlas grabbed his shirt over his chest. The fabric clung to sweat and blood. Underneath, his heart felt like it was trying to punch through bone. Each thump echoed through his arms, a syncopated drumbeat, too fast, too deep. Like a countdown. No… like a warcry.

’What the hell is happening to me?’

[Jormungandr blood is reacting]

That name again. Jormungandr. A word that tasted like cold metal and venom in his mouth. A snake without a cage. A name too ancient to belong in his veins.

His blood wasn’t his anymore. It churned. Heavy. Viscous. Molten. Like liquid fire laced with teeth.

He held out his hand and stared.

The veins had gone wrong. Not just glowing—but shifting. A sickly green bled beneath his skin, pulsing in waves that moved against his heartbeat. Like it had a rhythm of its own. A purpose.

One memory flickered:

Veil once said, “you have my mother’s blood, mixed with your own now, whether it’s a gift or a curse, time will tell, ”

He never asked what that meant.

Now he knew.

[Yggdrasil’s seed is reacting]

A deep pull unfurled from the pit of his stomach. Not pain—something worse.

Awakening.

Something ancient stirred in his soul’s hollow, where once there had only been wrath and purpose. The Seed. He hadn’t even known it was there until it bloomed—slowly, cruelly. Roots pressed out from his core, not physically, but psychically, threading through memory and mana both. They whispered in a language he couldn’t speak but understood.

Earth and ash.

Rot and rebirth.

He could smell it—bark burning, wet loam, the iron-tang of sacrifice.

Yggdrasil’s seed. Not healing him yet. Just witnessing. Judging. Waiting to see if he was worth saving.

[…..The Virus has stopped spreading.]

That chilled him more than the infection.

It hadn’t died.

It hadn’t weakened.

It had… paused.

Like a predator studying its prey. Like it had learned something new and was adapting.

The air around him shifted. The clearing, once filled with rushing, shouting soldiers, fell too quiet.

Even the birds stopped. No rustle in the branches. No wind through the trees.

A silence that listened back.

Atlas’s legs gave out completely.

His body folded like a marionette with cut strings. His face slammed into the earth, cheek grinding against stone and ash and blood. It didn’t even hurt—not because the nerves were gone, but because his body wasn’t sure how to feel anymore.

[Host’s Body is Weakened]

His muscles refused command.

His magic stuttered.

A shell of himself.

A frame that once cracked mountains, now cracking under its own weight.

He turned his head, dirt grinding into his gums. Grit in his teeth. Blood pooled in his mouth. His breath tasted like rust and regret.

“I’m… dying?” The thought didn’t panic him. It just tired him.

[Minor Healing activated (Perks of Yggdrasil’s Seed)]

[Healing… 0.1%… 0.4%…]

A flicker in the dark. A candle in a hurricane.

A warmth, small and defiant, sparked in his chest. It wasn’t fire. Not yet.

But it was something.

The Seed was trying to help. Thread by thread. Stitching back pieces of him like patching a torn myth.

He laughed—a brittle, broken thing that cracked in his throat.

0.4%.

“I’ve had hangovers heal faster,” he muttered, then coughed blood into the dirt.

He could hear voices around him. Faint. Distant.

Claire? Denish? Kury?

Did it matter?

They sounded far away, like echoes underwater.

He saw shadows approaching. Soldiers. Mages. Civilians.

They stared.

“Is he dying?”

“Is he melting?”

“No… he’s changing.”

He didn’t care.

Let them gawk.

Let them choke on their own fear.

He turned onto his back, barely breathing, and grinned through bloodstained teeth.

“…It’s okay,” he rasped. “Seems I got good genes.”

A lie. Everyone thought.

But lies were armor. And right now, he needed anything that wasn’t pain.

He opened his eyes, his blurry vision turning Normal.

And then he saw it.

His Truth Eyes—always sharp, always seeing—were struggling to make sense of what they now revealed.

A ripple in the air.

A blip of static, like reality glitching.

A shadow moved, slithering just beyond the visible spectrum.

Not his shadow. Not Claire’s. Not even a person’s.

Something that had no mass but all intent.

It passed the crowd. Ignored their fear. Slithered toward the treeline.

The mist was waiting there.

Crimson.

Churning.

Alive.

Not gas. Not smoke.

A wound in the fabric of the world.

And then—like a trigger pulled—

Three knights dropped from it.

Their armor shimmered like oil on water.

Visors mirrored nothing.

They didn’t hesitate.

“Did those fuckers just… go in?” Atlas whispered, voice brittle.

His Truth Eyes screamed.

The red mist wasn’t idle, it wasn’t just a field of virus—it was hungry. It was just pretending to be still.

But before he could analyze more.

The mist dissolved.

Not faded.

Consumed.

Like something inside was eating it.

Atlas’s stomach twisted, knotted, flipped.

The Emperial knights didn’t flinch.

Didn’t move.

And yet, the mist vanished around them.

’…What the fuck… what the actual fuck?’

“They knew….They fucking knew about the virus….the consequences …Empire’s playing with shit it doesn’t understand,” he muttered.

Ancient curses.

Fairy remnants.

Predators from forgotten gods.

And now—this?

He tried to rise.

Tried to call on his speed. The lightning. That electric flow that used to make time blur.

But his legs cracked.

Like twigs underfoot.

He face-planted again.

Agony tore through his spine, stabbing up into his skull.

[Host’s Body is Weakened. Body healing 0.8% finished]

“Fucking hell,” he hissed.

He clawed at the dirt, every movement a mile.

“No, no no no….don’t tell me I got fucking nerfed.”