Almost at the exact instant Zephyr finished speaking, at the very last syllable, the old man moved.
This man who had once stood at the peak of marine combat power shot forward, his entire figure exploding into motion.
Unlike the trainees from the Marine School of Justice, his charge did not create any dramatic noise. There was no loud crack of the air at his feet, no shattered stone in his wake. Yet his speed was on a completely different level, something those trainees could not even begin to compare to.
In the time it took to blink, Zephyr appeared right in front of Aren. His right fist, fitted with a prosthetic, swung toward Aren with absolutely no restraint, a straight, brutal punch.
The fist ripped through the air so violently it sounded like it was tearing it apart, a low growl howling through the atmosphere.
Whoosh.
At the moment the punch neared Aren's face, he remained as calm and expressionless as ever, only tilting his head slightly to the side.
Zephyr's fist passed right by his cheek, at the precise distance where even the force of the wind could no longer harm him.
For a brief moment, Aren's usually indifferent expression flickered with the smallest hint of change. He stepped backward, his body leaning just so, as invisible air currents seemed to gather under his feet. In a light retreat, he slid two or three meters away.
"Because your other arm is also a prosthetic, Instructor Zephyr, I was thinking of using just one hand to fight you. It appears I was being a bit naive."
Aren raised his hand and brushed his cheek. He had not been touched, but he could clearly feel the ferocity and weight carried even in the wind of that punch.
Hearing this, the corner of Zephyr's mouth curled upward. He glanced down at his right arm, then looked back up at Aren. "Hahahahaha. Then I really ought to thank you, brat. However..."
As that word fell, Zephyr clenched both fists, and his aura exploded.
Bang.
The stone beneath his feet shattered under the pressure of that surging presence.
Zephyr tightened his fists and fixed his gaze on Aren. "However, this old man is far from the point where I need pity from a brat like you."
Again.
Almost as soon as he finished, the old man rushed at Aren a second time.
This time, Aren did not simply stand and wait. The moment Zephyr launched himself, Aren's figure vanished from where he stood.
There was a thunderous boom as the two clashed head on, neither of them retreating even half a step. Fist met fist with a deafening crack.
Knuckle against knuckle.
Eyes locked onto eyes.
In the next instant, they both withdrew their fists, then struck out again.
Bang. Bang. Bang.
The sound of impact echoed above Marineford.
Each invisible collision between the two produced a powerful shockwave that blasted outward in all directions.
The trainees lying on the ground nearby were blown further away by the force of it. The stone slabs of the harbor shattered apart, fragments flying, while the marines watching all around felt their hearts tremble in their chests.
To all of them, Zephyr was still Zephyr. Even if he was over seventy years old, even if he had lost his right arm and worn a prosthetic in its place, in their hearts he was still Black Arm Zephyr, the marine admiral once known as the Admiral Who Does Not Kill.
A marine admiral was someone who stood upon the absolute summit of marine strength. Even a retired admiral was still terrifyingly powerful.
Everyone watching could see that Zephyr was not even fighting with his full strength yet.
Even so, Aren, this special recruit, was fighting him evenly. In fact, it was clear that Aren himself had not gone all out either.
"Mastery of aura, is it?"
As Zephyr threw a punch at Aren, Aren did not block it head on. With a slight twist of his body, he slid past the blow, letting it scrape past space where he had just been.
"Something like that. Although... I would not call it mastery."
As Aren's fist clenched, a visible swirl of air like a miniature whirlwind suddenly coiled around his knuckles. In the next moment, his fist shot toward Zephyr.
Zephyr raised his left forearm and took the blow directly.
"To fight like this without using Haki, and without the aid of any Devil Fruit power, relying only on your own body and the skill honed through training and experience... Old man or not, I am liking you more and more, Aren."
The moment he said that, Zephyr's left arm bulged with explosive strength, and his fist slammed toward Aren's face.
Aren's fist once again became wreathed in unseen currents of air, swirling wildly until they formed a massive vortex around it. Without any thought of dodging, he drove his fist forward to meet Zephyr's.
Boom.
The shockwave erupted.
Out at sea, the water exploded into surging waves that crashed hard against the warships and the harbor wall.
On the port, Aren's relatively small fist collided with Zephyr's massive one.
Facing Aren, Zephyr's smile never once faded. If anything, he grew even more exhilarated. Aren's strength had completely surpassed his expectations. He had thought the boy was an uncut stone that needed careful polishing. He had not anticipated that he was actually a piece of fine jade that demanded delicate, precise craftsmanship.
Zephyr could tell that what Aren was using was definitely not Devil Fruit power, and certainly not Haki.
Which meant that if Aren learned Haki in the future, whether Observation or Armament, or even awakened Conqueror's Haki, mastering even one type would make his strength undergo a complete transformation.
Hope.
Looking at Aren now, Zephyr was not just excited. In the young man, he seemed to see the future standard-bearer of the new generation of marines.
The future hope of the Marines themselves.
"If you daze off like that, I will end you, Chief Instructor Zephyr." Aren spoke coolly as he looked at him.
"Hmph." Zephyr let out a low laugh. "Then come and try, brat who has no idea how high the sky truly is."