The Heroine is My Stepsister, and I'm her Final Boss

Kaelion flew like a wound torn open across the horizon.

His body blurred with lightning, rage scorching the air itself. Every strike of his power left scars in the clouds, but none of it burned away the shame clinging to him like tar.

He had been chained.

He had been wounded.

By mortals.

Every pulse of his divine heart screamed for vengeance. His silver hair, still sticky with ichor, whipped in the wind as his thoughts spiraled darker, deeper.

The old man first.

Merlin. His cracked lips and vile laugh. The demi-god imagined ripping the sorcerer apart slowly, stripping flesh from bone, keeping his tongue alive just long enough to scream blasphemies before silence claimed him forever.

Then the women.

The young one—blue haired one, with her spear and her foolish grin. He would make her kneel, break that pride, turn the fire in her eyes into ash.

The sword-bearer—white one. Her blade had tasted his blood; he would return the favor, carving her a thousand times, forcing her to wield steel against those she cared for until her will shattered.

And the witch. Purple bitch. Her whispers had clawed his mind, dared to command divinity. He would chain her mouth shut, force centuries of silence until madness consumed her.

Yes. That would be their fate. Eternal torment. Mortals existing only to serve as his toys.

But as he descended upon a barren stretch of hell, scorched wasteland cracked and broken under the storm, his thoughts faltered.

Because something moved.

Not a demon. Not a specter.

A small, mundane creature.

A cat.

Its fur was coal-black, sleek despite the ash around it. Its tail swayed lazily as if the storms of a demi-god meant nothing. And its eyes—golden, not like coin but like molten sun—looked directly into Kaelion's.

Unflinching.

Unbroken.

Unmoved.

The demi-god froze, instincts tightening like a trap around his chest.

A cat? Here? Impossible. Mortal animals did not belong in Hell. Nothing survived here without corruption, without change. But this creature—this cat—was whole, pristine. And those eyes… those human-like golden eyes… they pierced him.

Kaelion snarled, shaking off the unease. "...You dare."

His voice shook the ground, yet the cat merely tilted its head.

"You dare look at me?" He roared. "I will grind you into nothing, beast."

His foot rose, glowing with lightning. He swung—

But the cat was gone.

Not fled, not darted—simply gone. A blink, a slip of reality. And when Kaelion turned, the weight of something brushed against his shoulder.

The cat sat perched there, tail curling around his neck like a scarf, eyes gleaming with mockery.

Mockery.

Kaelion's breath hitched. Rage, sharper than ever, exploded. He grabbed, fingers like talons closing—

The cat slipped. Always just beyond reach. A flicker here, a flicker there, landing on his forearm, his head, the ground, his shoulder again.

Each time, the golden eyes stared into him.

Each time, his chest grew tighter.

"You—" Kaelion spat lightning, bolts that split mountains in war. The sky cracked open with his fury, storms flung like weapons. But the cat wove between them, as though lightning itself bent aside, refusing to touch it.

"Enough!" Kaelion bellowed, summoning a spear of pure storm in his hand. He hurled it with all the fury of his bloodline, enough power to level citadels.

The cat didn't move.

It only blinked.

And then—its body began to glow.

Not with lightning, nor fire, but with an inner light. Red-hot, searing from within, every vein of its small body lit like rivers of flame under skin. Its golden eyes widened, and its mouth began to open. Wider and wider.

Kaelion staggered back. Something primal screamed at him. A warning. A terror no god-blood should feel.

The cat's mouth stretched wider—too wide, impossibly wide, splitting like a wound in reality. And inside…

Kaelion saw.

He saw a pit. A void. And within that void, shapes writhed—hands, faces, mouths screaming. Screaming endlessly.

He staggered back, in horror, "wh...what is this....what are you, WHAT THE FUCK ARE YOU!!!"

Now nothing. A fragment of memory, screaming in the maw of this impossible beast.

"No…" Kaelion whispered, lightning faltering around his body. His heart quivered. "No! This is a trick. A trick!"

But the screams grew louder, echoing inside his skull. The golden light flared, and for the first time in his existence, Kaelion trembled.

And then—only the scream. His own.

It tore across the wasteland, a sound not of rage but of raw, choking fear.

When the sound ended, the cat sat alone on the blackened rock. It licked its paw, tail swishing casually.

It burped.

Far away, back at the ridge of ruin, Lara crouched, scanning the ground. Her blue hair fell in her eyes, her voice carrying a note of worry.

"Where is it? Where's the cat?"

Eli wiped her blade, eyes sharp but softer now. "I saw it… right before Kaelion vanished. It just… Disappeared."

Claire, brushing ash from her violet robes, sighed. "It's not ordinary. Nothing with those eyes is ordinary."

Merlin groaned from where he sat propped against a rock, clutching his ribs. "Yes, yes, the bloody cat. Forget the near-death sorcerer, forget my bones grinding into dust—chase after your precious furball!"

But none of them listened.

"Here, kitty…" Lara called softly, voice carrying hope. "Come back…"

Merlin scowled. "By all the hells, it's probably a demon. Or worse. You're begging to pet death itself."

And then—a shadow leapt.

The cat landed before them, tail flicking, golden eyes gleaming. For a heartbeat, the three women froze. Then Lara gasped, breaking into a wide smile.

"There you are!"

She scooped the creature into her arms. Its fur was warm, almost too warm, but it purred against her chest. Eli reached to scratch behind its ears, and even Claire allowed herself a small smile as the animal nuzzled into Lara's grip.

"Soft," Eli murmured.

"Strange," Claire corrected, though her hand still stroked the fur.

The cat closed its eyes, content. Then—

Burp.

A faint echo rumbled from its throat. For a moment, Lara swore she heard a scream buried inside it, faint and far away. But then it purred again, and she laughed, dismissing it as imagination.

Merlin groaned louder, dragging himself up with his staff. "Wonderful. The great battle of our age, and my companions have been reduced to cat-sitters."

No one replied. The three women hugged the cat as though it were treasure.

And the cat's golden eyes flickered once more.

Watching.

Always watching.