The six months leading up to the Magic Knights Entrance Exam were a blur of shadows and shockwaves. While Asta spent his days screaming through physical labor, Karl retreated into the deepest parts of the Hage forest, near the skeleton of the ancient demon.
His goal was simple: survival and control. He didn't have a mentor like Whitebeard or Blackbeard to teach him. He had to invent everything from scratch, using his memories of the story as a rough blueprint.
The Early Months: Trial and Blood
The first time Karl tried to manifest the Tremor (Quake) power, he nearly shattered his own arm. The vibration didn't just exit his fist; it traveled backward. If not for his Immortal Body, his bones would have been permanently pulverized.
He noticed that as he grew, his mana capacity didn't just increase—it mutated. It became denser and heavier than normal mana. Every day, his body would break slightly under the strain of his own power, only to heal back stronger, expanding his "mana tank" until he felt he could finally eclipse Yuno's massive natural reserves.
The Duel of the Prodigies
Two weeks before leaving for the Royal Capital, Yuno found Karl in a clearing.
"I can't sense your limits anymore, Karl," Yuno said, his Four-Leaf grimoire floating open. "Let's see how far you've really come."
Yuno didn't hold back. "Wind Magic: Swift White Hawk!"
A massive bird of pressurized wind dived toward Karl. Karl stood his ground, his two-page grimoire opening to the first page.
"Darkness: Absorb."
Karl raised his left hand. A curtain of swirling, purple-black darkness manifested. When the wind hawk struck the curtain, it didn't explode—it was simply deleted. The darkness acted as the ultimate anti-magic barrier, swallowing the spell whole.
"Too slow," Karl muttered.
He didn't walk; he used Vibration Step, a technique where he emitted micro-shocks from his soles to launch himself forward like a bullet. In the blink of an eye, he was in Yuno's blind spot.
Yuno reacted instantly, spinning with a wind blade, but Karl was faster.
"Darkness: Universal Pull."
An invisible gravitational force erupted from Karl's palm. Yuno felt his entire body yanked forward, his wind magic unravelling as it was pulled into the void. Karl caught him by the collar, his palm glowing with a dark hum that nullified Yuno's remaining mana.
"I win," Karl said with a kind smile, releasing the pull.
Yuno landed, breathing hard. "You're... one step ahead of me. No, maybe more."
The Arsenal: 8 Foundations
By the end of the six months, Karl had successfully developed eight core techniques—four of the Void and four of the Quake—designed to be used without destroying himself.
[The Void Arts (Dark-Dark Fruit Essence)]
Absorb: A defensive cloak that 'eats' incoming magic and projectiles.
Universal Pull: A gravitational vacuum that drags enemies toward his palm.
Black Hole: He spreads darkness on the ground, sinking everything in a specific radius into a void.
Void Bind: Using dark energy to create ropes that don't just tie an enemy, but silence their mana.
[The Quake Arts (Tremor-Tremor Fruit Essence)]
Air Crack: A basic punch that shatters the air, sending a kinetic shockwave forward.
Vibration Step: High-speed movement by vibrating the air beneath his feet.
Shatter Point: Touching an object (or a magical barrier) and vibrating it at its resonance frequency until it turns to dust.
Internal Tremor: A low-frequency tap that sends vibrations through an opponent's body to bypass armor and strike their internal mana flow.
The Road to the Royal Capital
The trek across the Clover Kingdom was a long test of endurance. Asta was a ball of energy, running on his hands or carrying heavy rocks, while Yuno hovered elegantly on his wind. Karl walked at a steady pace, his hands in his pockets, but every step he took seemed to ripple the ground beneath him, propelling him forward with minimal effort.
The Encounter with the High-Borns
Near the central gates, a group of minor nobles on brooms tried to force them off the road. "Out of the way, peasants! You're getting dirt on our robes!" one sneered, aiming a gust of wind at Asta.
Karl didn't even stop walking. He simply tapped his foot on the ground.
"Tremor: Air Crack (Minor)."
A subtle vibration traveled through the air, hitting the nobles' brooms. The wood didn't break, but the mana stabilizing them shattered. All three nobles went face-first into the mud.
"The wind is quite choppy today, isn't it?" Karl said, walking past them without a glance.
The Encounter with the God of Destruction
Upon reaching the Capital, the trio was overwhelmed by the sights and smells of the massive city. While Yuno went to register, Asta found himself in a "dispute" with the local Anti-Birds.
"Gah! Get off me! Why are they only biting me?!" Asta screamed, running around like a madman.
In his panic, Asta slammed headfirst into a wall of muscle. A massive man with a black cape, a cigar, and a face that looked like it was carved from a thunderstorm looked down.
"Hey, kid," the man growled. It was Yami Sukehiro, Captain of the Black Bulls. "You trying to die? Because I can help you with that."
"I-I'm sorry! You just looked like you had a lot of space, so I—" Asta started babbling.
"Shut up," Yami said, grabbing Asta's head with one hand and lifting him off the ground. "I'm in a bad mood. I lost a lot of money on cards, and now some brat is using my chest as a landing pad."
Karl stepped forward, his expression neutral but his eyes sharp. He could feel Yami's Dark Magic—it felt similar to his own, but more "physical," whereas Karl's was "void-based."
"Captain Sukehiro," Karl said, his voice calm. "My brother is an idiot, but he's a hardworking one. I'd appreciate it if you didn't crush his skull before the exam even starts."
Yami stopped, his dark eyes shifting from Asta to Karl. He let out a puff of smoke, his gaze narrowing as he sensed the "weight" coming off the quiet boy. "And who the hell are you? His babysitter?"
"Just another candidate from Hage," Karl replied, not backing down an inch from the Captain's killing intent.
Yami smirked. He dropped Asta, who tumbled to the ground gasping for air. "You've got balls, kid. And your mana... it smells like a hole in the dirt. Interesting." He turned away, waving a hand dismissively. "Don't fail the first test, or I'll kill you both for wasting my time."
Arrival at the Exam Arena
The registration was a formality. Asta showed his black book, Yuno his Four-Leaf, and Karl his thin, two-page one-leaf.
"Number 166," the clerk snorted. "Go on, peasant. Try not to get hurt."
As they entered the massive colosseum, the Anti-Birds swarmed the arena. Hundreds of them dived at Asta, forming a massive cloud of pecking beaks. They avoided Yuno entirely.
But as Karl walked through the center of the stadium, the birds that dived toward him suddenly screeched in terror and veered away. It wasn't that he had no mana—it was that his mana felt like a predator. The Void within him made the birds' instincts scream danger.
High above, the nine Captains took their seats.
"What a noisy brat," Nozel Silva muttered, looking at Asta.
"But look at the other two from that village," Fuegoleon Vermillion noted. "The one with the Four-Leaf... and the one sitting in the corner with the two-page book. The birds won't even go near him."
Yami leaned back, his boots on the railing. "That's the one I told you about, William. He's got a body like a mountain and a grimoire that looks like it's missing its soul. This is gonna be fun."
Karl looked up, his hands in his pockets. He felt the Tremor power itching in his right hand and the Darkness pulsing in his left.
'Six months of training,' Karl thought. 'Time to see if the Magic Knights are ready for a one-leaf disaster.'