Growing up as Illumi's twin was like living in the shadow of a mountain. No matter how hard Dean tried, no matter what he accomplished, there was always an immense presence looming above him, casting everything else into darkness.
From the earliest days of training, it was clear that Illumi was the superior twin in almost every measurable way. He was faster, more precise, more efficient. He absorbed the family's teachings with an ease that bordered on supernatural, as if the techniques of assassination had been encoded into his very DNA. By the time they were both eight years old, Illumi could kill without hesitation, without the slightest tremor in his hands, without any visible sign of internal conflict or moral struggle.
Dean, on the other hand, struggled in ways that went far deeper than mere physical capability.
The physical training was manageable. His body adapted quickly to the rigorous exercises, his reflexes sharpened with each passing day, his strength grew steadily if not spectacularly. He could run for hours without tiring. He could perform acrobatic feats that would have been impossible for a normal child. He could lift weights that seemed far too heavy for his small frame. But the physical aspect of training was only the surface. Beneath it lay something far more challenging: the philosophy of it all.
The Zoldyck family's training wasn't just about teaching techniques. It was about fundamentally reshaping a person's psychology, stripping away the natural human impulses toward compassion and mercy, replacing them with cold, calculating efficiency. It was about teaching children that human life was cheap, that emotions were weaknesses to be eliminated, that the only thing that mattered was becoming strong enough to kill without hesitation.
And Dean couldn't do it.
Oh, he tried. He performed the exercises. He practiced the techniques. He killed the animals they brought to him, learning to do it with increasing efficiency. But there was always a part of him that rebelled against it, a voice from his past life that whispered that there had to be a better way, that strength didn't have to come at the cost of one's humanity.
"You're thinking too much," Illumi said one afternoon during a sparring session in the training courtyard. The older twin moved with fluid grace, his movements economical and deadly, like a predator that had been hunting since birth. "Kill or be killed. There is no middle ground. There is no room for hesitation or doubt."
Dean blocked a strike that would have torn his arm off if it had connected. His younger body moved on pure instinct, muscle memory from his past life combining with the training he'd received in this one. But he used his superior reach to create distance between himself and his brother, buying himself time to think, to plan, to find a way to counter Illumi's relentless assault without matching his twin's raw aggression.
"There's always a middle ground," Dean replied, his breathing controlled despite the intensity of the sparring match. "There's always another option. The best assassins aren't the ones who kill without thinking. They're the ones who understand their targets, who can predict their movements, who can accomplish their objectives with minimal force and maximum efficiency."
Illumi's expression didn't change, but his attacks became more vicious, more personal. He was trying to prove a point, Dean realized. Trying to demonstrate that sentiment was a liability, that emotion was a weakness that would get you killed.
Dean drew on knowledge from his past life, techniques that seemed to come from nowhere but felt absolutely right when he executed them. Instead of meeting Illumi's force with force, he redirected it, used his brother's own momentum against him. It was a small victory, a momentary advantage in a much larger conflict, but it was something. It was proof that there were ways to be strong that didn't require abandoning everything that made you human.
"Interesting," Illumi said, pulling back from the sparring match. His eyes were calculating, analyzing, trying to understand how his supposedly weaker twin had managed to counter his technique. "Where did you learn that?"
"I figured it out," Dean said, which was technically true, though it was a heavily edited version of the truth. The knowledge had been there, buried deep in his memories, waiting for him to discover it and adapt it to his current situation.
Illumi studied him for a long moment, and Dean could see the calculation happening behind his twin's eyes. Illumi was trying to understand him, trying to categorize him, trying to figure out whether Dean was a threat or simply a curiosity. And whatever Illumi concluded, it wasn't positive.
"You're defective," Illumi said finally, his voice carrying absolute certainty. "Father was right about you. You lack the proper mindset for an assassin. You're too soft. Too emotional. You'll never be as strong as me, and you'll never be a true Zoldyck."
The words stung, but not because Dean believed them. They stung because they were partially true. He was different from Illumi. But different didn't necessarily mean weaker. It meant something else. Something that even Dean didn't fully understand yet, but something that he sensed could become his greatest strength if he could figure out how to develop it properly.
"Maybe," Dean said, meeting his twin's gaze with a calmness that seemed to unsettle Illumi. "But I'll become strong in my own way. And when I do, you'll understand that strength comes in many forms."
Illumi turned away, and Dean could see the dismissal in his posture. To Illumi, Dean was already irrelevant. A failure. Someone to be pitied or ignored, depending on Illumi's mood. The older twin had already written off his younger brother as incapable of achieving greatness, and nothing Dean said or did would change that assessment.
The rest of the family seemed to agree with Illumi's evaluation. Silva and Kikyo watched Dean's training with expressions of mild disappointment, as if they were witnessing the slow confirmation of their worst fears about their second son. His younger brother Killua sometimes joined the training sessions, and even he seemed to understand instinctively that Dean was the weaker twin, the defective one, the one who didn't quite fit the Zoldyck mold.
But Dean didn't let it break him. Instead, he used it. He used his status as the weak twin to observe, to think, to develop strategies that Illumi's direct approach couldn't counter. He studied the family's assassination techniques not to replicate them perfectly, but to understand them, to find their weaknesses, to develop alternatives that might work better in certain situations.
And slowly, gradually, he began to notice something strange happening inside his body. An energy that seemed to flow through his physical form, responding to his will, growing stronger with each passing day. It was faint, almost imperceptible, like feeling your own heartbeat if you concentrated hard enough. But it was there, and it was undeniable.
By the time Dean was twelve years old, he was beginning to understand what it was. Nen. The power that flowed through all living things. The power that could make an assassin truly deadly. The power that the knowledge from his past life had been preparing him to understand and master.
And unlike Illumi, who had been trained to use Nen since childhood according to the family's rigid methods, Dean was discovering it on his own, through his own will and determination. He was learning to feel it, to understand it, to manipulate it in ways that were uniquely his own.
The defective twin was becoming something far more dangerous than anyone in the family realized.
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