Chapter 3: Practicing Assassin Arts X First Meeting of Brothers
What is cognition?
In essence, it is the sum total of everything you have ever seen, heard, thought, and experienced. It is the complete mental framework built from perception, memory, and emotion.
In his past life, Roy had watched Demon Slayer. He had projected himself onto its characters, felt their joy, their sorrow, their rage, and their despair. Because of that deep emotional investment, the story had left an indelible footprint on his soul—his cognition.
Mulling this over, he pushed himself up from the snow. As he did, a small cloth pouch fell from his gi, spilling a few pieces of candy onto the white ground. The sight jogged his memory: today was a celebration for his youngest sister, Hanako, who was now one month old.
His presence here had altered the timeline. Tanjiro was no longer the eldest son. Rokuta, the original youngest, had not yet been born. This meant he was two or three years before the start of the canon plot.
Not only was his father, Tanjuro Kamado, still alive and well, but so was his grandmother—the kind, white-haired old woman who would often hold Tanjiro while watching the stars.
It was a strange parallel. In reality, Roy was the eldest son of the Zoldyck family. In his world of cognition, he was the eldest son of the Kamado family. Perhaps it was this "resonance" between his two lives that allowed him to open the door to this specific world.
Roy sensed a connection there. He bent down, picking up the candies one by one, before beginning a full diagnostic of his current state.
First, Nen.
Roy focused, attempting to channel the aura within him. He directed the flow towards the tip of his right index finger. A faint, milky-white glow appeared. It was weak, and barely visible against the bright snow, but it was unmistakably there.
A wave of relief washed over him.
After all, this world, much like the world of Hunters, was no paradise. It was a world stalked by man-eating demons. Having Nen, especially before he could master any Breathing Styles or acquire a Nichirin Blade, was a critical advantage.
Next, the Assassin Arts.
Shadow Step, Rhythm Echo, and Snake Awakens.
Narrator's Note: Shadow Step is the foundational movement technique of the Zoldyck family, built on four principles: Silence, Weightlessness, Deception, and Illusion.
To move with the lightness of a swallow, with the phantom-like unpredictability of a dream. Roy took a single step and his body seemed to dissolve into motion. He became a ghost, gliding through the ancient forest, shifting east then west, his form a blur among the trees. He moved so perfectly that he left not a single footprint in the deep snow.
This surreal display completely stunned a certain someone who had come looking for him, worried that his big brother was out in the woods after dark.
Today was Hanako's celebration, and their father, Tanjuro, had sent his eldest, Eiichiro, down the mountain to buy supplies. When he hadn't returned by dusk, their mother, Kie, sent Tanjiro—the one with the nose like a bloodhound—to find him.
Tanjiro found his brother, alright. But the sight broke his brain.
The earnest, kind-hearted boy was bundled in a thick, green-and-black checkered haori, a light purple scarf wrapped around his neck. He stood frozen in the falling snow, his beautiful amber eyes reflecting the ghostly, dancing figure of Roy. The words "Big bro..." were caught in his throat.
A single thought repeated in his mind: Is... is that really my brother Eiichiro?
It was. It was one hundred percent his brother.
His eyes could be deceiving him, but his nose never lied. Tanjiro twitched his nose, confirming the familiar, gentle scent of his brother. Convinced, he quietly ducked behind a large tree, peeking out with just his head.
Meanwhile, Roy, having finished his warm-up with Shadow Step, didn't pause to rest. He immediately began practicing Rhythm Echo.
This assassin technique was, in essence, an advanced application of Shadow Step. It added a powerful layer of misdirection to confuse the opponent.
Roy took a deep breath and moved again. In an instant, a circle of after-images blurred into existence around his starting point, each one looking as solid as the real him.
It was the same technique Killua had once used against Chairman Netero while trying to steal the ball on the airship. Of course, Netero was on another plane of existence entirely, far beyond what a rookie who hadn't even learned Nen could ever hope to touch.
But that was Isaac Netero, the strongest human alive. This was just Tanjiro, a boy who had never seen a real fight in his life.
Seeing this, Tanjiro's eyes went wide. He started dumbly counting on his fingers, trying to figure out how many brothers he suddenly had. He was so absorbed that he didn't notice the sharp shiiink sound until it was too late.
A razor-sharp hand was embedded in the tree trunk right next to his ear.
Narrator's Note: Snake Awakens is the art of conditioning one's hand into a blade of peerless sharpness. At the novice level, it can pierce solid wood. With mastery, it can shatter stone. At its peak, it is said to be able to sever even Nen-forged weapons.
Roy had personally witnessed Silva use a single hand-chop to slice a masterwork katana in two.
He himself was still at the beginner stage. Sinking his hand a few inches into the wood was his current limit. Anything more would require years of brutal conditioning. His proficiency in sensing killing intent, however, was another matter; a lifetime of being surrounded by it had taught him a thing or two.
He had sensed Tanjiro the moment his younger brother had found him.
Roy pulled his hand from the deeply gouged tree trunk and turned to the familiar yet new face of his brother, a warm smile on his face. "Mother sent you to find me, didn't she? Sorry, I fell asleep for a bit. Didn't mean to make you all worry."
Tanjiro stared at Roy's face, then glanced at his brother's unharmed hand, then back at the hole in the tree. He was breathing, but his mind hadn't caught up yet. He nodded dumbly, then shook his head violently like a rattle.
Roy found his dazed expression amusing and ruffled his hair. "Got a lot of questions, huh?"
Tanjiro shook his head again, then nodded.
Roy's smile widened.
"Today is Hanako's special day," he said gently. "Let's go celebrate with her first. We can talk later, okay?"
Tanjiro nodded emphatically.
Roy patted his shoulder, said no more, and with a flick of his foot, scooped the hand-axe into his grip. He then bent down, hoisted the basket of charcoal onto his back, and began walking towards home.
Tanjiro followed closely behind, his mind buzzing. He walked in a daze until the moon had risen above the treeline, stretching their shadows long across the snow.
He finally stopped when Roy did.
Through the curtain of snow, they could see the familiar cluster of small wooden cabins. A gentle wisp of smoke rose from the chimney of the easternmost cabin. They could faintly hear the laughter of children and the sound of an adult coughing. It was the very picture of a warm, peaceful mountain home.
"It's a shame," Roy whispered, almost to himself. "...in this world, demons are real. In two or three years, none of this will exist."
Tanjiro looked up at him, confused. "Demons?"
But his older brother clearly didn't want to explain. With another glance, he started walking again, heading for the warmth of home.
Tanjiro blinked, tightened his scarf, and hurried to catch up.
As they approached, the sound of their footsteps brought the family to the door. Seeing Roy and Tanjiro, the younger children cheered.
There was Nezuko, Takeo, and Shigeru. And the youngest, still a babe in arms, Hanako, held securely by their white-haired grandmother.
"Eiichiro-niichan, you're back!"
"Yeah," Roy replied with a genuine smile. "I'm back."
His gaze met that of a man sitting on the edge of the veranda. The man coughed a few times, his hands fiddling with a set of ceremonial robes. Seeing Roy looking at him, he offered a gentle, welcoming smile of his own.