The Demon king's Last oath

The week after Lucian found Caius in the library passed in strained silence. The brothers spoke little, though Julian, in his usual cheerful way, tried to smooth things over. Lucian remained cold and distant, his sharp gaze often flicking to Caius as though waiting for him to slip.

Caius, on the other hand, maintained his usual composure. His days were spent in quiet observation, and his nights in further study, digging through the estate's ancient texts for any hint of the growing power inside him—or the forces hunting him.

But the tension wasn't just with Lucian. The Marquess had started to watch Caius more closely, his calm but calculating eyes following him whenever they crossed paths. Lady Helena, blissfully unaware of her husband's suspicions, continued doting on Caius, but even she seemed unsettled by the distance growing between her sons.

It was only a matter of time before the cracks widened.

One crisp morning, the Marquess gathered his sons in the training yard. The estate guards had set up dummies and wooden weapons, the air buzzing with anticipation. Lucian, as the eldest, stood confidently at the center, a wooden sword resting on his shoulder. Julian fidgeted nearby, clearly less excited about the session.

Caius stood slightly apart, his hands clasped behind his back as he observed.

"This is an important skill," the Marquess began, his voice firm. "As sons of House Thorne, you must be able to defend yourselves. Lucian, you've been training for years, so I expect you to set an example."

Lucian grinned. "Of course, Father."

"Julian, you'll practice with Lucian today." The Marquess's gaze then fell on Caius. "And you, Caius… it's time you learned as well."

Caius's expression didn't change, but his mind raced. "A test." His father's tone, his lingering gaze—it wasn't just about learning swordsmanship. The Marquess was watching for something.

"Do you understand?" the Marquess asked.

"Yes, Father," Caius replied, his voice calm.

The Marquess handed him a smaller wooden sword. It was light and well-balanced, but Caius felt the weight of the situation more than the weapon.

"Lucian, start with Julian. Caius will observe for now."

Lucian nodded, turning to his younger brother with a smirk. "Ready to lose again, Julian?"

Julian groaned but took his position. The two began sparring, their movements uneven but spirited. Lucian's strikes were calculated and precise, while Julian's were wild and frantic, his frustration mounting with every failed counter.

As Caius watched, he analyzed their movements. Lucian favored a high guard, leaving his left side vulnerable. Julian's swings were powerful but poorly timed, creating openings in his defense.

It was all so… predictable.

After several rounds, the Marquess called a halt. Julian collapsed onto the grass, panting, while Lucian stood over him, triumphant.

"Enough," the Marquess said, his eyes turning to Caius. "Your turn."

Caius stepped forward, the wooden sword resting lightly in his hand. He met Lucian's gaze, noting the glint of arrogance in his brother's eyes.

Lucian smirked. "Don't worry, little brother. I'll go easy on you."

Caius didn't respond. Instead, he took his position, his stance calm and balanced.

The Marquess raised a hand. "Begin."

Lucian lunged, his strike fast and deliberate. But Caius sidestepped effortlessly, the wooden sword in his hand moving with precision. His counter was light, a calculated tap to Lucian's exposed side.

Lucian froze, his smirk faltering.

"What—?"

Before he could recover, Caius stepped forward again, his movements fluid and controlled. Another strike—this time to Lucian's wrist—forced him to drop his sword.

The training yard fell silent.

Julian sat up, his mouth agape. The guards watching from the sidelines whispered among themselves. Even the Marquess seemed momentarily taken aback.

Lucian, however, was furious. His face reddened as he snatched up his sword and charged again. "You just got lucky!"

This time, his strikes were wild, driven by anger rather than skill. But Caius remained composed, his small frame weaving effortlessly around Lucian's attacks. He didn't strike back immediately, instead allowing Lucian to exhaust himself.

When Lucian's footwork faltered, Caius stepped forward, disarming him with a single, decisive blow.

Lucian stumbled, his sword clattering to the ground.

Caius lowered his weapon, his blue eyes steady as they met Lucian's. "You leave your left side open," he said simply.

Lucian clenched his fists, his pride wounded. "You—"

"Enough," the Marquess interrupted, his tone sharp. He stepped forward, his dark eyes fixed on Caius.

"Where did you learn to fight like that?" he asked, his voice calm but probing.

Caius met his father's gaze, his expression unreadable. "I watched. And I remembered."

The Marquess frowned, his suspicion deepening. "That level of skill doesn't come from just watching."

Caius said nothing, his small hands tightening around the hilt of the wooden sword.

That evening, the tension in the household was palpable. Lucian avoided Caius entirely, while Julian hovered nervously, unsure how to bridge the growing rift between his brothers.

The Marquess, however, sought solitude in his study, his thoughts heavy.

He poured himself a glass of wine, staring at the flickering flames in the fireplace. Caius's performance on the training field replayed in his mind. There was no hesitation in the boy's movements, no trace of fear or inexperience.

It was as if Caius had done it a thousand times before.

Helena entered quietly, her soft footsteps pulling him from his thoughts. "What's troubling you?" she asked, placing a gentle hand on his shoulder.

"Caius," the Marquess admitted. "There's something… unnatural about him."

Helena frowned. "You've been saying that for weeks. He's just gifted, that's all."

The Marquess shook his head. "It's more than that. The way he moves, the way he looks at things… It's as if he's older than he seems."

Helena smiled faintly. "You're being paranoid. Caius is a sweet boy. He just takes after you more than the others."

The Marquess didn't respond, his thoughts too tangled to voice.

Alone in his room, Caius sat by the window, his wooden sword resting against the wall. His mind replayed the training match, his control over his movements, his restraint.

"It's growing stronger," he thought, his blue eyes glowing faintly in the moonlight. "I can't keep hiding it forever."

He glanced at his hands, the faint memory of the flame from that night in the garden lingering at the edges of his mind.

"If Father suspects me… if Lucian keeps pushing…"

He closed his eyes, exhaling slowly.

"I'll need to leave the estate. The answers I need aren't here."

But as the night deepened, Caius felt it again—that faint pull in the distance, like a thread tugging at his very being.

Something—or someone—was drawing closer.