Seven days passed.
For the other examinees, these seven days were a living hell of starvation, insomnia, and constant fear.
For Su Chen, it was a camping trip with occasional pest control.
When the sun rose on the seventh day, only four people stood at the clearing at the base of the mountain.
Tanjiro, Kanao, Zenitsu, and Genya.
And, of course, Su Chen.
While the others were covered in dirt, dried blood, and exhausted to the point of collapse, Su Chen looked irritatingly pristine.
His clothes were slightly torn from his battle with the Hand Demon, but he had bathed in a stream, eaten hot meals from his [Infinite Storage], and slept in a portable tent he kept in his inventory.
"Welcome back," the Ubuyashiki twins intoned in unison. "Congratulations on surviving."
Tanjiro was leaning heavily on a stick, barely staying upright. He looked at Su Chen, stunned. "Su Chen-san... you look... refreshed?"
"Pacing is part of survival, Tanjiro," Su Chen lied smoothly.
In reality, Su Chen had spent the last six days hunting down every Tier-2 demon on the mountain to farm EXP.
He was now Level 4.
His [Flesh Manipulation] proficiency had risen to "Beginner - Grade 3," allowing him to harden his skin to the density of rock instantly.
"You must now choose the ore for your Nichirin Sword," the white-haired twin said, gesturing to a table filled with rough, ugly stones.
Su Chen stepped forward.
To the naked eye, they all looked like rocks.
But Su Chen activated [Spirit Sight] and [Olfactory Sense].
Sniff.
Most rocks smelled like cold iron. Some smelled like dirt.
But one rock, buried in the corner, had a scent like ozone and deep ocean pressure. It hummed with a frequency that vibrated against his retinas.
"I'll take this one," Su Chen picked up the jagged, heavy ore.
He didn't put it in his storage. That would expose his ability. He handed it to the twins like a normal person.
However, the moment his skin touched the ore, he mentally commanded:
System, Analyze and Copy Material Structure.
[Target: Scarlet Crimson Iron Sand (High Purity)]
[Structure Recorded.]
[You can now synthesize this material in the Storage using Spirit Energy.]
Su Chen suppressed a grin. He didn't just get one sword. With this blueprint, he could mass-produce Nichirin swords back on Earth for his future army.
Return to Sagiri Mountain.
The journey back was grueling for Tanjiro, but Su Chen walked with a light step.
When they finally reached the hut, the door burst open.
Nezuko, who had been sleeping for two years, stumbled out. She didn't look at Su Chen. She ran straight to Tanjiro.
"Nezuko!" Tanjiro dropped his box and collapsed, hugging his sister. Urokodaki dropped his firewood, running over to embrace them both. tears streaming down his mask.
It was a beautiful, heartwarming scene.
Su Chen stood ten meters away, leaning against a tree, watching quietly. He didn't interrupt. He was the outsider, the traveler.
But he was also the opportunist.
System, Scan Target: Kamado Nezuko.
[Target: Kamado Nezuko (Awakened)]
[Race: Unique Demon (Sunlight Resistance Developing)]
[Affection Level: Neutral (0/100)]
[Copyable Attributes:]
Exploding Blood (Blood Demon Art):Ignites the user's blood into magical flames that burn only demons/poison.
Size Manipulation:Can shrink or grow body mass.
High-Speed Regeneration (Superior):Much faster than average demons.
"Copy: High-Speed Regeneration (Superior) and Size Manipulation."
[Copying...]
[Success.]
Su Chen felt his cells bubbling. His earlier [Lesser Regeneration] merged with this new one, evolving into [Intermediate Regeneration]. Now, he could probably regrow a finger in an hour.
As for [Exploding Blood], he hesitated. That art required demonic blood to function. As a human, copying it might be useless unless he mutated his own blood. He saved it for later.
That Night.
The celebration was over. Tanjiro and Urokodaki were asleep, exhausted from the emotional day.
Nezuko, however, was awake.
She sat on the porch, staring at the moon, her legs swinging. The bamboo muzzle was still in her mouth.
Su Chen stepped out of the shadows.
He didn't make a sound, but Nezuko turned instantly, her slit pupils locking onto him.
She growled low in her throat—a defensive instinct.
"Easy," Su Chen whispered, raising his hands. "I'm not an enemy."
He sat down on the porch, keeping a respectful distance.
He knew Nezuko was hungry. She regained energy by sleeping, but the craving for human flesh was a constant torture she fought against.
"You're hungry, aren't you?"
Nezuko didn't answer. She just stared at him. Or rather, she stared at his veins. Su Chen's blood, enhanced by the Wolf Meat and his high stats, smelled delicious to her.
"You can't eat humans," Su Chen said softly. "But..."
He flipped his hand.
From his [Infinite Storage], he pulled out a small, translucent red crystal.
It wasn't human flesh.
It was a Mutated Beast Heart Core from a Tier-1 creature on Earth, processed and crystallized. It contained massive vitality but zero human DNA.
"Try this," Su Chen rolled the crystal across the floorboards.
Nezuko stared at the glowing red marble. It smelled... rich. Like life. But it didn't smell like a person. It smelled like a wild animal.
Her instincts took over. She grabbed it and popped it into her mouth (bypassing the muzzle somehow, or maybe she just absorbed the energy).
Crunch.
Her eyes widened.
The energy rush was pure and clean. The gnawing hunger in her stomach vanished instantly, replaced by a warm, fuzzy feeling of fullness.
She looked at Su Chen. The wary growl stopped.
Her eyes curved into a happy expression.
[System Notice: Nezuko Kamado Affection +10]
[Current Status: Curious / Friendly.]
"Good girl," Su Chen smiled, resisting the urge to pat her head. Not yet. "If you behave, I have more of those."
He stood up and went back inside.
He wasn't trying to steal her from Tanjiro as a brother. He was planting a seed. In the future, when he was ready to leave this world, he would offer her a choice: stay here and hide from the sun, or come with him to a world where she could walk in the daylight (once he solved her condition).
But for now, feeding the waifu was enough.
15 Days Later: The Swordsmith Arrives.
The sound of wind chimes announced the arrival of a very eccentric man wearing a sunflower mask.
"I am Haganezuka! I have forged the sword for Kamado Tanjiro and Su Chen!"
He ignored everyone and sat down, unpacking the blades.
"Come on, come on, draw them!"
Haganezuka vibrated with excitement. "I want to see the red blade! A Child of the Sun must have a red blade!"
Tanjiro drew his sword first.
It turned pitch black.
"BLACK?!" Haganezuka screamed, tackling Tanjiro. "Why is it black?! That's unlucky! I wanted to see red!"
After Urokodaki pulled the angry smith off the poor boy, Haganezuka turned to Su Chen, panting.
"You! You picked a very strange ore. Very dense. Draw it!"
Su Chen stepped forward.
He gripped the handle.
He channeled his energy. Not just the Water Breathing, but a trace of the Spirit Energy he had cultivated and the chaotic energy from his Mutated Constitution.
Sching.
The blade slid out of the sheath.
Slowly, the color began to change at the hilt, spreading to the tip.
It wasn't blue like Giyu's.
It wasn't black like Tanjiro's.
It turned a deep, shimmering Indigo, so dark it looked like the bottom of the ocean where light couldn't reach. But along the edge, there was a faint, jagged line of Silver-White, crackling with static.
"Ooh..." Haganezuka stopped thrashing. He leaned in close. "Indigo? Deep Sea Indigo? I've never seen this shade. And the edge... it looks like it's vibrating."
"It suits me," Su Chen said, giving the sword a few experimental swings.
The blade felt heavy, but balanced.
When he swung it, there was no sound. The air parted silently.
[Weapon Acquired: Nichirin Sword (High Grade)]
[Attribute: Fluidity & Severing.]
[Note: Conducts Spirit Energy at 120% efficiency.]
"Good sword," Su Chen nodded.
Just then, a Kasugai Crow flew down, landing on Tanjiro's shoulder.
"Caw! Orders! Orders! Tanjiro Kamado! Su Chen! Head to the Northwest Town! Girls are vanishing! Hunt the demon! Caw!"
Tanjiro looked determined. "Our first mission!"
Su Chen sheathed his Indigo blade.
"Northwest Town... The Swamp Demon," he recalled. "Three bodies. Creates a swamp dimension. Drops... Space-attribute items?"
His eyes narrowed.
Space-attribute abilities were rare. If he could copy the Swamp Demon's ability to create a pocket dimension (Swamp), he might be able to merge it with his Storage or use it for combat traps.
"Let's go, Tanjiro," Su Chen adjusted his fox mask. "I have some collecting to do."