This truly was Yemu's only signature technique.
As mentioned earlier, Yemu's ultimate path lay in striving for peak proficiency in every ability, leaving no weaknesses. Yet this proved highly improbable. Unless one possessed extraordinary genius, human energy remained finite—it was impossible to excel in every aspect.
If Yemu had had the luxury of time before mastering Haki, after receiving the training methods for Haki and swordsmanship from Rayleigh, he was forced to make a choice.
Strength, speed, vitality, defense, physical techniques, swordsmanship, Devil Fruit abilities, Armament Haki, Observation Haki, Conqueror's Haki—the cultivation of each demanded an immense investment of time.
He understood the folly of trying to grasp too much, yet he refused to abandon any single pursuit. Thus, he found his time growing ever more scarce.
He had no desire to wait until his twenties or thirties to venture out onto the open seas. Therefore, he altered his training approach, ceasing to devote excessive effort to cultivating any single ability in isolation.
Whether it was developing his Devil Fruit powers, refining his sword techniques, honing his physical arts, or delving into Haki.
He abandoned the pursuit of dazzling techniques and skills, instead grasping the essence of all power. He centered his efforts on cultivating both body and will.
The body is the physical form; the will is the spirit.
Training the body raised the ceiling for all abilities, pushing the limits of strength time and again.
Training the will strengthened the spirit, enhancing control over power with each breakthrough.
The result of such cultivation is that within the limits of Yemu's body and will, he can wield his strength with absolute freedom.
Be it Devil Fruit abilities, physical techniques, swordplay, or Haki.
Therefore, Yemu now has no need to specifically train in any particular moves or skills. Many of his techniques, as long as they fall within the scope of his body and will, can be executed simply by conceiving them—truly at will.
But one technique stands apart.
This technique is the only one he truly dedicates himself to training: the Flame Dragon Prison Fire Fist.
It pushes both the Mera Mera no Mi's power and Armament Haki to their absolute limits, then fuses the two to unleash maximum destructive force.
This technique was inspired by our protagonist Luffy's idea for Yemu in the story.
Though the exact mechanics remain unclear, it's evident that Haki's counter to Devil Fruit users differs from the effects of seawater or Seastone.
While seawater and Seastone impose near-total suppression on Devil Fruit users, Haki's restraint functions more as an indirect limitation.
This explains why Devil Fruit users, when affected by Sea Stone or seawater, not only lose their powers but also experience a significant physical weakness.
However, when a Devil Fruit ability is restrained by Haki, the ability is simply nullified—without causing weakness or exhaustion.
In fact, within the story, Luffy is able to use both Haki and his Devil Fruit abilities simultaneously.
This gave Yemu the inspiration to combine the Mera Mera no Mi's powers with Haki.
Thus, this technique was born: Flame Dragon Prison Fire Fist.
...
Whoosh...
In an instant, Bullet's body shot upward, the immense strength causing the ice beneath him to shatter like a spiderweb.
Yemu clenched his fists and charged toward Bullet.
But after hours of fighting, Yemu's stamina was nearing its limit. Especially with this technique, his speed and strength were far from their peak.
Both his Armament Haki and the Mera Mera no Mi's abilities fundamentally relied on his physical endurance.
Bullet instantly sensed this, his eyes widening as he grinned in mockery.
"Hahahaha... So you were just bluffing? With that speed and strength, how could you possibly hit me..."
As if answering his own words, Bullet effortlessly dodged Yemu's punch, bending low and aiming a blow straight for Yemu's abdomen.
But almost immediately, something felt off.
Because this strike had actually connected squarely with Yemu's midsection.
No—or rather, Yemu hadn't dodged at all.
"What!? Why?"
Though he knew Yemu's stamina was already dangerously low, this punch shouldn't have been unavoidable.
Moreover, Yemu hadn't been knocked back by the strike.
Just then, an overwhelmingly dangerous feeling surged through him from the side.
"Flame Dragon Prison Fire Fist."
"What!?"
Bullet turned his head in disbelief, only to see a black fist, now enveloped in crimson energy, transform into a roaring dragon head, charging toward him.
Bullet's body instinctively reacted.
"Whoosh..."
He swiftly retreated, but even then, a sharp pain shot across his face.
Lowering his gaze, he saw his cheek was burned.
It hadn't even hit him directly, and he had quickly covered his face with Armament Haki.
Yet, as the fire-fist grazed his skin, the explosive heat seared his face, leaving behind a painful, charred sensation.
"...Impossible... How did it break through my Armament Haki..."
Bullet stared at the scorched mark below his eye, unable to believe it.
The pain wasn't enough to make him cry out, but mere seconds after he had declared that Yemu could spare his life if he could break through his Armament Haki defense and injure him, he had been proven wrong in an instant.
And in that split second, for the first time, he felt unease—his body instinctively reacting with a reflex to retreat.
To him, this was a tremendous disgrace!
"Impossible... impossible... such a weak punch..."
"I am the strongest..."
The man who had always prided himself on being the strongest had been the first to retreat in this fight.
Bullet's roar echoed across the entire Ice Island and surrounding seas, sending a wave of shock through the Sky Pirates.
"Hey, now's not the time to lose your mind. The fight has only just begun..."
"The flames on my fist aren't ordinary flames. They're hellfire, ignited by the concentrated energy of my entire being—enough to incinerate anything it touches. Its temperature is even higher than magma."
"Even if it only grazes you, the instant of extreme heat will shatter your Armament Haki defense."
"This move was originally meant for that Magu Magu no Mi user in the Marines, but it looks like you're getting an early taste..."
"I told you—next, I'm going to hit you..."
Placing victory in the hands of the enemy's mercy was clearly unreliable, so Yemu prepared to continue.
But his time was running out. The Flame Dragon Prison Fire Fist required immense stamina to maintain both Armament Haki and the intense heat on his fists.
In that moment, as his Armament Haki shattered, Bullet's expression twisted into something more savage.
"No... Impossible... I won't lose..."
With a furious roar, Bullet's dark, Armament Haki-covered arms radiated a crimson, flowing aura.
Yemu froze.
This was the technique Rayleigh had mentioned—a skill surpassing even the highest level of Armament Haki—one Yemu himself had yet to master.
The coiling of Conqueror's Haki!
Yet, Yemu didn't hesitate. He poured every last ounce of his strength into his fists, holding nothing back.
His stamina had already reached its absolute limit. This was his final strike.
And just as he readied himself, he suddenly heard a strange sound.