Ironwall Port slowly faded into the morning mist.
The Oro Jackson slipped past the reef fields and returned to open sea.
At the stern, Bullet sat cross legged on the deck with his eyes closed.
He was using highly focused Observation Haki to sense the state of his own body.
Inside him, the black core continued its slow, steady pulse. With each beat, tiny currents of energy flowed out, nourishing muscles, bones, and organs.
Some of that energy came from normal food and rest.
But most of it now was the converted material energy from the metal he had devoured off the Anvil three days earlier.
He opened his eyes and lifted his right hand.
With a thought, black scales surfaced on the back of his hand and spread up to his forearm.
Under the morning sun, the scales were no longer just dull matte black. A very faint metallic sheen shimmered across their surface.
Bullet extended the index finger of his left hand and scraped it hard across the dragon scales.
A harsh screech rang out, but the scales were completely unmarked.
He grabbed a training knife lying beside him. It was just a steel practice blade, hardly a famous sword, but sharp enough.
He swung it down with force.
Clang.
A small chip appeared on the knife's edge. The dragon scales were still pristine.
"Hardness is up around fifteen percent. Toughness even more... about twenty."
Bullet muttered.
"And..."
He clenched his dragonized right fist and slowly tightened his grip.
The muscles of his arm bunched and swelled. The tiny gaps between the scales shifted subtly with that motion, constantly adjusting to maintain perfect fit and coverage.
That was another hidden benefit of devouring metal.
The scales' self adapting ability had improved.
Before, when he transformed, the scales had been more like a layer of armor laid over his skin.
The defense had been strong, but there was always a faint resistance when joints moved.
Now, the scales felt like part of his body. They changed shape in real time with his movements.
"Devouring metal strengthens the dragon's hardware."
Bullet drew his conclusion.
"And devouring living matter strengthens the human life core."
"Only with both together is the evolution complete."
He released the transformation. The scales flowed back into his skin.
At the very last moment, as they completely vanished, he caught a detail.
Faint dark gold markings were more clear on his skin than before, like fragments of an ancient pattern.
...
"Bullet."
A steady voice came from behind him.
Bullet turned to see Rayleigh walking over.
"Mr. Rayleigh."
Rayleigh sat down beside him.
"Testing your new gains?"
Bullet nodded.
Rayleigh looked out over the sea, his tone even.
"That black flame of yours. How heavy is the cost?"
Bullet answered honestly.
"Three blasts burned through about ten percent of my stamina."
Rayleigh's eyes narrowed thoughtfully.
"But the power is terrifying."
"I saw that metal being... broken apart."
"Rather than broken apart, it is more like devoured."
Bullet explained.
"The black flame is highly compressed devouring energy. When it touches matter, it absorbs it."
"But the conversion rate is not high. Around thirty percent."
"Thirty percent is already frightening."
Rayleigh said.
"If one day you can push that rate higher, even reach full absorption..."
He did not finish, but Bullet understood.
If the Black Flame Dragon Breath ever reached the point where it could completely devour everything it touched, that would be a truly world ending power.
Where it passed, all things would return to nothing.
"That is why I came to you."
Bullet looked straight at Rayleigh.
"I need to get stronger. Faster."
Rayleigh raised a brow.
"With the speed you are growing, it is already plenty fast."
"Shanks has been training like a madman these last few days. You rattled him."
"Not enough."
Bullet shook his head.
"Pirates like the Iron Hammer crew can no longer put enough pressure on me."
"I need stronger enemies, but before that, I need to patch a weakness."
"Oh?"
"What weakness?"
"Internal defense."
Bullet pulled his cloak aside, revealing his bare, solid chest.
He tapped the spot over his heart.
"In dragon form, my external defense is very strong."
"But my internal organs are still the weak point."
"If I face someone whose blows can pierce the scales, or who can attack my insides directly..."
He let the sentence hang, but Rayleigh had already followed the thought.
"You want to learn internal lining."
Rayleigh said.
"Internal lining?"
"A more advanced application of Armament Haki."
Rayleigh stood.
"Think of Haki as armor."
"Beginners can only cover the surface, like wearing a sheet of iron."
"Experts can let Haki seep inside and form a second layer of protection over muscles, bones, and organs."
"That is internal lining."
He went below for a moment and returned carrying two glass cups and a bottle of rum.
Rayleigh set the cups on the deck side by side and filled them both.
"Watch closely."
He extended his right index finger and gently tapped the outside of the left cup.
Armament wrapped his fingertip. The glass shuddered faintly, but did not break.
"This is external defense. Protecting the cup from being shattered."
Then he moved his hand, placing his palm above the cup without touching it.
Bullet could clearly sense a thin layer of Haki spread from Rayleigh's hand, pass through the glass, and coat the inner surface evenly.
"This is internal lining."
"Even if the outer wall cracks, the lining can still hold the liquid in for a short time."
"Of course, that is not how you use it in a fight."
Rayleigh withdrew his hand.
"Once you learn internal lining, your defensive system will be complete."
"The scales on the outside are the armor. The Haki inside is the buffer."
"Even if the armor is pierced, that buffer will blunt the attack significantly and protect your vitals."
A glint of understanding flashed through Bullet's eyes.
"I see."
"Teach me."
Rayleigh smiled.
"This sort of technique usually takes years, if not more than a decade of Haki practice to master."
"But you..."
He did not finish, but the meaning was obvious.
Bullet did not fit into normal standards.
"First, you need more delicate control of your Haki."
Rayleigh sat cross legged again.
"Close your eyes and feel the flow of your Armament inside your body."
Bullet did as he was told.