Eren was enjoying the rare peace at Aunt Denise's house. His parents had left early that morning, likely to visit the guild or the soldiers—his father had only just regained consciousness after a long rest, but that didn't stop him from heading out. This meant Eren could finally catch a break from the constant whirlwind that was his neighbor's daughter, Tria. The energetic girl, with her endless questions and high-pitched voice, drained him more than he cared to admit. At Aunt Denise's, he could sit quietly by himself, away from the storm of social interaction.
Sitting near the window, Eren gazed out at the bustling street. The sun hung low in the sky, casting golden rays across the busy marketplace. Eren's mind, however, wasn't on the activity outside. He was preoccupied with his own frustration, the ever-present feeling that he was being left behind in a world that demanded strength and skill.
Lately, he'd been reflecting on his magic—what little he knew about it, anyway. In his past life, he'd read countless stories and novels that mentioned how magic was channeled through meridians, mana cores, and various other concepts. Eren was certain that, like the protagonists in those tales, he must have a mana core hidden somewhere inside him.
But there had been no sign of it so far. He'd asked his parents about it before, but they had always told him he was "too small" to understand such things. He hated that answer. In his past life, he had been an adult, a person with knowledge and understanding. Now, it felt like he was stuck in a body that refused to cooperate with his mind.
He had tried to meditate, to sit quietly and focus on sensing the magic flowing through his body. But the more he tried, the more frustrated he became. Nothing happened. No sensation, no spark of energy—just a dull silence inside. His hands twitched with a desperate need for something—anything—that would show him he was on the right path.
Yesterday, after seeing his father wounded, something inside him snapped. If he didn't start developing strength now, if he didn't find a way to unlock his magic, how would he protect anyone he cared about? The world was dangerous. And the fact that his father had nearly died—it hit harder than anything Eren had ever experienced. That need for strength burned in him like a fire.
He couldn't ask Aunt Denise for help. She wasn't exactly the magical expert he needed. Besides, she'd only make him play with Tria, and that was the last thing Eren wanted. There was also Ley—the lazy, indifferent cat contracted to his mother. Eren had tried asking the creature for advice once, offering it a piece of fish from his plate. All Ley had done was eat it and lazily say, "Just do it."
"Just do it?" Eren had almost laughed in disbelief. Was that supposed to be advice? Was that how magic worked in this world? "Just do it?"
As the hours passed and the sun began to dip below the horizon, Eren's mind wandered back to his parents. What had really happened yesterday? He wanted to know, but they always kept him at arm's length when it came to adult matters. He wasn't a kid anymore, not in his mind, anyway.
His thoughts were interrupted by the familiar figure of Ley, who lay sprawled out lazily on the garden windowsill, eyes half-closed, his tail flicking now and then as if the world barely existed to him.
Suddenly, something boomed in his mind.
System initiating spontaneously due to the user accomplishing a high-grade achievement at such an early age.
Eren almost jumped out of his skin. His heart skipped a beat. "What...?" He blinked, trying to process what just happened. He had heard of systems before—most protagonists in his past life had some sort of system or notification interface that helped them grow stronger, but he had never expected anything like that to happen to him. At least, not at this age. He was barely two years old!
His hands trembled with excitement, and for a moment, he forgot everything else. Maybe... maybe his years of trying to sense mana had finally paid off. Maybe the system had been triggered by his efforts. He could feel a sense of accomplishment rise in his chest, but it was quickly replaced by a surge of anticipation.
"Open achievements," he muttered to himself, the words feeling strange as they left his lips.
The moment he thought it, a hyper-realistic screen appeared before his eyes, hovering in midair. Eren gasped at the sight. The screen was sleek and sharp, with glowing blue text that felt as real as if it were physically in front of him.
All the achievements were listed as question marks, except one. The first one.
Achievement: Come into contact with a being from the Shadow World. Reward: To be Decided.
His breath caught in his throat. A being from the Shadow World? He frowned, staring at the achievement in disbelief. How had he come into contact with something from the Shadow World? He had been sitting here, in Aunt Denise's house, staring out the window all day. He hadn't gone anywhere, hadn't met anyone new, and yet the system was telling him that this had just happened.
His mind raced, trying to piece things together. How? He looked around the room, his gaze sweeping over every corner. Had I done something? Or... had someone come into contact with me?
A cold chill ran down his spine, but the answer didn't come. Not yet.
Then, the screen flickered, shifting to red as an emergency quest appeared.
Emergency Quest: Survive the attacks of the Shadowborne.
His heart stopped.
It clicked then—they came to me. The Shadowborne were after him. He didn't have to go anywhere. They were already here, hidden in the shadows.
Eren's breath hitched in his chest. The realization dawned on him with a shocking clarity. They are in my shadow.
Before he could even process his next move, a cold, dark presence slithered from the edges of the room, wrapping around him like a suffocating fog. Eren's heart pounded in his chest. It's happening!
He didn't even think about it—his body reacted before his mind could catch up. Without a second thought, he leaped out the window, heart hammering in his chest as he shouted for Ley.
"Ley!" he screamed, panic flooding his voice. His small legs kicked through the air, but all he could focus on was the sensation of something lurking just behind him, stretching toward him.
His breath caught in his throat as he saw it—the tentacle. It shot out from the shadow beneath him, a pitch-black, writhing thing that moved with unnatural speed. It was sharp, its form coiling as it sought to strike.
Eren's stomach dropped. There was no time. It's too fast. I can't dodge it!
Just as the tentacle was about to stab him, he felt a sharp, intense pressure in the air.
Slash!
The air around him cracked, and the tentacle was cleaved clean through. Eren's body jerked violently as several hair-like extensions shot out from somewhere and latched onto him midair. Before he could comprehend what was happening, the tendrils pulled him with a force so strong that his stomach lurched and his breath caught in his throat.
What's happening? Who's pulling me?
Eren was suspended for a moment, his heart thudding against his ribs, as he was pulled until a familiar, furry back appeared beneath him.
"Ley!" he exclaimed, his voice cracking with relief.
It was Ley, his mother's lazy, indifferent cat. But something was wrong. This wasn't the usual, chubby, lazy cat that Eren had known. No, this Ley looked entirely different.
Eren's wide eyes traced the large, muscular front paw that he could see from above. As Eren clung to Ley's back, the transformation began to unfold before his eyes.
First, it was his arms. What had once been soft, chubby limbs, were now bulging with raw power. The fat melted away, revealing thick muscles that seemed to pulse with newfound strength. The fur along his arms thickened and darkened, almost shimmering under the faint light, as his claws elongated, sharpened, and gleamed with an ominous black sheen at the tips. They weren't the round, harmless claws of the lazy cat Eren had known; now, they were deadly weapons—long, sharp, and capable of shredding through anything in their path.
Next, Ley's chest expanded. The rounded, soft belly that had always hung low like a well-fed house cat's, began to harden and firm up, growing in size and muscle definition. Eren could see the muscles rippling under the fur, strong and well-defined, as Ley's body reshaped into that of a powerful apex predator. The fat that once padded his frame was now replaced with a thick, firm layer of muscle, giving Ley a broad, imposing chest that looked like it could withstand any blow.
His back followed suit. The once slouched, lazy curve of his spine straightened as the muscles along his back grew in size, creating a long, powerful silhouette that seemed built for speed and strength. Eren could feel the powerful tension in Ley's back as he moved, the kind of strength that made it clear Ley could leap, run, and fight with the force of a much larger creature.
Ley's legs, too, began to change. What had once been short, stubby limbs became long, sinewy pillars of muscle. His hind legs lengthened and thickened, the muscles becoming taut and defined as they took on the raw strength needed for swift, explosive movements. His paws—once soft and cute—became powerful and massive, each paw growing in size, the pads toughening, and the claws extending into menacing black talons. The fur around his legs stood up more rigidly now, as if charged with the power of the earth itself.
The most dramatic change, however, was in Ley's face. His once chubby, sleepy expression turned ferocious as his features elongated, the muscles of his jaw and face sharpening. His eyes, once half-closed in laziness, now blazed with an intense, wild ferocity. His mouth stretched open, revealing sharp teeth, each one as lethal as his claws, glinting in the dim light like knives.
The final transformation was his fur, which, while still thick, grew darker around the edges, turning into a mix of deep brown and jet-black streaks. The once fluffy fur was now sleek and taut, as if every strand had been woven for maximum mobility and strength. His entire body seemed to hum with power, each movement exuding the confidence of a king, the ferocity of a predator on the hunt.
Ley, the chubby, lazy cat, was now unrecognizable. Before Eren stood a massive, muscular brown tiger with rippling muscles, razor-sharp claws, and an aura of strength so intense that the air around him seemed to crackle with electricity. He was a terrifying force—a far cry from the adorable pet he once was. Now, Ley looked every bit the part of a legendary beast—ferocious, untamed, and fully capable of taking down any enemy in his path.
As Ley stood there, towering over the house, his voice rumbled deep in his chest, laced with power and authority. "What are these pests from the Shadow World doing here?" he growled, his claws flexing in anticipation.
And Eren, still in shock, couldn't help but feel a wave of awe wash over him. He had never imagined Ley, his lazy, chubby childhood companion, could transform into something so powerful, so terrifying. He was no longer just a cat—he was a force of nature.