Kaien sat in the ruins of the plaza, Oblivion Fang still humming faintly as if unwilling to rest. His hands trembled around the hilt, though the battle was over. His reflection in the shard of glass haunted him: violet flames still flickering faintly in his eyes, shadows coiled around his arm as if refusing to let go. He had won, yes—but the victory felt like a chain tightening around his throat. He could not forget the masked child's words, the way its voice had slipped into his mind with such certainty. The Abyss is not your weapon. The Abyss is your master.
Kaien clenched his jaw and forced the whisper down. "No," he muttered, dragging himself to his feet, "I am no one's weapon." He sheathed Oblivion Fang and started walking, ignoring the ache that pulled at his muscles. The night air was heavy, suffocating, but it was quieter now. The demons had retreated—or perhaps, after watching, they had decided he was not prey tonight.
But someone else was watching.
From the rooftops above, a shadow shifted. Kaien's instincts screamed, and in one smooth motion he drew his blade again. "Who's there?" His voice cut through the silence like steel.
A figure dropped lightly from the rooftop, landing soundlessly on cracked pavement. The figure was tall, cloaked in black with a silver insignia etched across the chest—two crossed swords wrapped in chains. The hood slid back, revealing a young man with short dark hair and sharp, calculating eyes that glimmered with something between suspicion and amusement.
"You swing your blade like someone who's been killing demons for years," the stranger said, his tone calm but firm. "But I've never seen your face among the Slayers. Who trained you?"
Kaien didn't answer immediately. He kept Oblivion Fang raised, the blade whispering softly in his hand. "Who are you?"
The stranger smirked. "I'm not your enemy. Not unless you want me to be. My name is Ren Kurogane. Demon Slayer, First Division." He let the title hang in the air like a badge of pride. "And you, boy, are either the greatest rookie I've ever seen… or the most dangerous mistake this city's ever birthed."
Kaien frowned, lowering the blade just slightly but not enough to drop his guard. Ren's words cut close to the truth. Dangerous. That was what he feared becoming. Still, his eyes narrowed. "You followed me."
Ren chuckled. "You light up the night like a beacon. Even the blind could follow the trail of shadows you're leaving behind." His smirk faded into seriousness as he added, "But don't misunderstand. I didn't come to help you. I came to see if the rumors were true."
Kaien stiffened. "Rumors?"
Ren's gaze sharpened. "A boy in the city who fights like a Slayer but wields a power darker than the demons he kills. Tell me, Kaien Draven… whose side are you really on?"
The tension between them was suffocating. Kaien's grip tightened on Oblivion Fang. He wanted to shout that he was human, that he was fighting to protect the world, not to destroy it. But the memory of the shadows binding him, the whisper in his head, the violet glow in his eyes—it all lingered like a curse. Could he truly claim he was different from the monsters he cut down?
Before he could answer, the ground beneath them trembled. Both Kaien and Ren spun, senses flaring. A guttural roar erupted from the edge of the plaza. From the cracks in the earth, another demon clawed its way out—massive, horned, with wings torn and dripping ichor, its body a fusion of beast and shadow. Its voice was a rasping growl, filled with hatred. "Slayyyer… Slayerrrr…"
Ren's expression hardened instantly. He drew his twin blades, steel flashing in the moonlight. "Looks like the night's not done with us yet." His eyes flicked to Kaien. "We fight together. Unless you'd rather die proving a point."
Kaien said nothing. He lifted Oblivion Fang, the violet fire sparking back to life. The demon roared again, leaping toward them, claws tearing into the earth.
The battle erupted like lightning.
Ren moved first, a blur of motion, his twin blades crossing to parry the demon's strike before cutting deep into its leg. The creature howled, its shadows lashing out like tendrils, trying to wrap around him, but Kaien was already there. His blade slashed across its chest, burning shadowfire into its flesh. The monster reeled, wings flapping violently, throwing rubble into the air.
Kaien and Ren fought as if they had known each other for years. Ren's style was fast, precise, surgical—each strike calculated to cripple. Kaien's was raw, overwhelming, each swing of Oblivion Fang cracking the ground and setting the night aflame with purple lightning. Together, they cornered the beast, their blades crossing in rhythm.
But the demon was no simple prey. Its body rippled, shadows hardening into armor as it roared and released a wave of dark energy that sent both Slayers flying backward. Kaien slammed into the wall of a crumbling building, coughing blood, but he forced himself back up. Ren landed in a crouch, spitting dust, his eyes narrowing.
"This isn't just a demon," Ren growled. "It's a herald. The higher ranks are sending scouts now."
Kaien's heart sank. A herald? That meant this was only a taste of what was coming.
The demon roared again, spreading its wings. Black flames erupted across its body, and with a single beat of its wings it charged, faster than before. Kaien braced himself, shadows rising around him instinctively. For a heartbeat he hesitated—afraid of losing himself to the Abyss again—but then he saw Ren struggling to block the beast's strike, his blades straining against the monster's power. If he didn't act, Ren would be crushed.
Kaien let the darkness in.
The shadows surged, coiling around him like armor, his eyes blazing violet. He dashed forward, a blur of speed, and struck the demon with such force that its body twisted in mid-air. Ren wasted no time, slicing into its wings, severing one in a spray of black ichor. The monster screamed, crashing into the ground.
Kaien raised Oblivion Fang high. The shadows gathered at its edge, trembling, desperate to be unleashed. With a roar that tore his throat raw, he brought the blade down. The impact shook the plaza, shadowfire exploding outward in a violent shockwave. The demon shrieked as its body split apart, dissolving into ash that scattered into the night.
Silence fell. The two Slayers stood amid the ruins, their chests heaving, sweat and blood dripping from their faces.
Ren was the first to speak. His voice was low, steady, but his eyes were sharp. "That power of yours…" He sheathed his blades slowly. "It's not Slayer training. It's not human. You know it as well as I do."
Kaien said nothing. His chest still burned, his hands shaking from the shadows that had not fully left him.
Ren stepped closer, his gaze unflinching. "If you don't learn to control it, it will consume you. And when it does, I'll be the one to cut you down."
Kaien's eyes lifted to meet his. He saw no hatred there, no blind fear. Only truth. Only warning.
Ren turned, his cloak shifting in the wind. "The organization will want to see you. If you're smart, you'll come willingly. If not…" He left the words unfinished, walking into the shadows of the ruined street.
Kaien stood alone again, Oblivion Fang humming faintly in his hand. His thoughts were heavy, tangled. The Abyss stirred inside him, whispering still, eager for the next fight. He closed his eyes, tightening his grip on the sword.
He was no one's weapon. Not the demons', not the Abyss's, not the Slayers'.
But even as he swore it, he couldn't shake the truth Ren had spoken: the line between Slayer and monster was thinning with every battle, and soon, he might not be able to tell which side he stood on.
And somewhere deep in the dark, the watchers behind the crystal whispered again. "He has met the Kurogane boy. The threads tighten. Let the pieces fall into place. The King will rise, and the boy will either be our salvation… or our doom."