Reincarnated in DxD as Keiba With a Sword Bone

The room was a luxurious vision, but with a chilling air that spoke of its owner's devilish nature. The walls, a deep crimson, were adorned with intricate dark patterns that seemed to shift in the light, casting ominous shadows. Velvet curtains hung from the windows, blocking any trace of sunlight, enveloping the room in a perpetual twilight. Rich golden chandeliers hung from the ceiling, their flickering light illuminating the cold marble floors that seemed to echo every step. In the center of the room lay a massive bed, the sheets of black silk contrasting with the blood-red walls. The ornate furniture, crafted with elegant yet dark motifs, added to the eerie atmosphere of the space. It was a bedroom fit for someone with both power and darkness in their soul.

The boy opened his eyes, blinking rapidly as a sharp pain shot through his head. His thoughts felt disjointed, fragments of memories swirling like a chaotic storm. He groaned, his hand instinctively clutching his forehead. "Ahhh, why is my head hurting so much?" he muttered under his breath, his voice raspy and thick with confusion.

His gaze drifted across the room, but something felt off. The soft, plush feeling beneath him… "Wait, what is this soft thing?" His eyes widened, his mind struggling to piece things together. "A bed? But… I… was I not just...?"

Suddenly, the fragments of memories began to flood his mind. A flash of images—familiar faces, battles, names he couldn't quite place—overwhelmed him. "Ahhhhhh!" he gasped, clutching the side of his head as the memories began to intensify, like a painful torrent tearing through his consciousness. "Huhhh, huhhh..." He breathed heavily, his pulse racing. "What is this memory? It's… it's torturous..."

The names—"Kiba," "Kiba… Holy Sword Project… Rias Gremory, Akeno…" The words echoed in his mind, ringing with familiarity. He groaned in confusion. "Doesn't it look like it's Kiba's memory? But why do I have it?"

His eyes shot open in alarm as his thoughts swirled with panic. His chest tightened as he scrambled from the bed, feeling his body move with an unfamiliar fluidity. He spotted a full-length mirror against the far wall, the reflective surface calling to him like a beacon. Without thinking, he rushed toward it, his heart pounding in his chest.

As he stood before the mirror, he couldn't help but freeze, his eyes wide with shock. The reflection staring back at him was not his own, or at least not the one he remembered. Short blonde hair framed a face that was smooth and youthful, with a slightly angular jawline. His skin glowed with an unnatural smoothness, and his body—toned and lean—was far beyond anything he'd ever had before. The sheer presence of his reflection screamed something… otherworldly.

"I... I... What the hell?!" He stared at his reflection, his breath shallow as his eyes darted over the unfamiliar features. He touched his face, as if trying to confirm it wasn't just some dream. "I'm... I'm Kiba?! How is this possible?" His mind was racing, trying to comprehend what was happening. "But I was… I was there… I was checking that box… In that ancient site in China…"

His thoughts were a jumbled mess. "The box… I found it. Inside was a golden crystal..." His heart skipped a beat as memories of the past rushed forward. "Yeah, I remember now. I touched it… and then... everything went black…"

But suddenly, his body began to glow, a bright golden light that seemed to pulse and surge from within him. He gasped, feeling an intense heat spread through his body. "Wait a minute—what the hell is happening?" He doubled over, clutching his chest as pain surged through him. "Ahhh! It's... it's hurting!" His voice cracked with the intensity of the pain as his bones began to crack, shifting and contorting in ways he couldn't comprehend.

The sound of cracking bones filled the room, mingling with the rush of blood pounding in his ears. His heart felt like it was being torn apart and reconstructed at the same time, the pain agonizing, relentless. His entire body trembled, as though something far more powerful was forcing its way into him, changing him irrevocably.

"Ahh! Ahhhhhh!" The pain continued, every muscle, every cell, feeling like it was being reformed. He screamed as the transformation took hold, unable to control his own body. It felt as though time itself was slowing down, each second dragging on for what seemed like hours. His thoughts were a blur, each sensation sharp and overwhelming.

And then, after what felt like an eternity, everything stopped. He opened his eyes, gasping for breath, his body slick with sweat. Slowly, cautiously, he stood up. His legs felt stronger, more stable than ever before, as though they were grounded in the very earth itself.

He looked at himself in the mirror again, his mouth going dry. His body had undergone a complete transformation. He was smoother, more refined, almost ethereal—like something out of a fantastical world. His hair had grown longer, cascading down his back in soft, golden waves. His height had increased, his frame now exuding an aura of strength and vitality, boundless energy surging through him. He flexed his hands, feeling the raw power coursing through his veins, and marveled at the sheer force contained within his body.

But just as he began to process this new reality, his brain seemed to rebel once more. His head throbbed violently, a new wave of pain sweeping over him as his mind struggled to absorb an influx of new information. "Not again..." he moaned, clutching his temples, his face twisted in agony.

Memories, techniques, and powers—new knowledge poured into his consciousness, stabbing into his mind like knives. It was overwhelming, suffocating, but he held on. He clenched his teeth and focused, breathing through the pain. After several minutes, he finally managed to regain control, his breath steadying. He opened his eyes, a new clarity taking hold of him.

"I understand now," he muttered under his breath, his voice a little more composed but still tinged with awe. "The golden stone I found—it was a Sword Bone from a Sword Immortal, and now it's fused with me. I have golden bones, a golden heart... a Sword Heart." He said it with a strange reverence, realizing the gravity of what had just happened.

"And there's more," he continued, his mind racing as the knowledge settled within him. "My Sacred Gear... it's evolved into Eternal Sword Birth." He couldn't help but marvel at the sheer power of it all. "And... the chess piece Rias put in me... It's dissolved and reconstructed into a golden Sword piece. This... this gives me the same power as Rias's chess pieces." His lips curled into a smirk, the power within him awakening a new sense of confidence.

With a deep breath, he exhaled slowly, his body still humming with energy. "Now I have the ability to create my own group of swordsmen. 'Sword Bind.' It will bind them to me for eternity, through their souls. This power... it's too much." His eyes narrowed as he realized the weight of his new abilities.

Unable to contain his exhaustion, he flopped back onto the bed, closing his eyes. His body still hummed with energy, but his mind needed rest. "Haah... this is a lot to take in."

With a final, weary sigh, he succumbed to the darkness once again, the room quiet except for the faint echo of his breathing.