Armament Haki was a form of energy that was produced from stamina. That's why every time Luffy ran out of Haki, he would get extremely tired.
But while Haki was tied to stamina, it wasn't exactly stamina. Just like how Chakra was tied to stamina, but stamina wasn't Chakra.
If Chakra was the energy formed by merging spiritual energy and physical energy, Haki was about manifesting Willpower by consuming stamina.
That consumption would be triggered when a person's Willpower reached a certain stage, combined with his physical and mental capacity.
In other words, just like how Awakening required the mind and body to catch up to the powers of the Devil Fruit.
Haki required one's Willpower and stamina to catch up to a certain point where it could manifest.
Haki was simply Willpower being manifested.
Observation Haki was a radar that gave users the sixth sense of the world around them, allowing them to sense someone's emotions, presence, and strength.
But its most powerful use was precognition, allowing the user to sense an opponent's attack before they even launched an attack.
Armament Haki, on the other hand, was the manifestation of an armor around the body. This was done by using their own Willpower through the consumption of stamina.
But this whole process wasn't something that could be done in an instant. It required training.
Of course, in the heat of battle or in a life-or-death situation, this process could be instantaneous.
But only talented and trained ones had this opportunity. Otherwise, most people would awaken Haki instead of dying.
When Tyler thought about Armament Haki after reading its manual, he realized that it was similar to Yin-Yang Release from Naruto.
But instead of merging Yin and Yang Release into one, Armament Haki was about consuming stamina to form a new form of power within the body.
This kind of consumption would slowly increase one's stamina, thus increasing their upper limit as well.
That's why Haki could contend with some of the strongest Devil Fruits.
Not because Haki could negate their effects, but simply because the Haki user could constantly train their body by increasing their stamina upper limit.
Of course, there was also a negative effect to this. Just an increase in their stamina wouldn't improve their body.
They would need to train their physical body, but the training wouldn't be effective while using Haki.
That's why Garp trained without using Haki.
Because no matter how hard he trained, his body had reached the point where he could recover within a few hours or days.
But this kind of recovery required energy, and energy was stamina. So, this whole thing came full circle to Haki improving one's upper limit by increasing one's stamina.
As for their ability to negate Devil Fruit, it was simple. Haki was spiritual power. It was one's Willpower.
If one had enough Willpower, they could use it to dominate anything, including the Devil Fruit ability.
Tyler knew following the manual to lock his Willpower and actively release it outside his body was going to be difficult.
As stated before, Armament Haki was a new form of energy that emerged out of stamina. It was an aura that could be released outside his body.
So, how did one transform the stamina into this aura?
That was left out in the manual. Because there was no consistent method for this process. It was like how breathing works.
One could find a scientific method like how Vegapunk was able to do, but most people in this world couldn't.
And he didn't have the luxury to ask Vegapunk. So, Tyler could only come up with his own ideas.
One of the ideas written in the book was simultaneous release.
By actively releasing the idea of Willpower from his mind and consuming stamina through training, one could eventually lock into that process.
But he had something better. If one simply needed to lock into that process, couldn't he just find it with Observation Haki?
Haki was Haki.
It wasn't like Armament Haki required different energy than Observation Haki. The result would be different, but the process might not.
Both Observation Haki and Armament Haki consumed stamina. That's why only the trained users of Haki could keep their Observation Haki on all the time.
But Observation Haki also consumed less than Armament Haki. That's why Whitebeard could keep his Observation Haki on while sleeping.
But Garp couldn't. After all, Axe Hand Morgan made a name for himself by slashing Garp's chest and drawing blood.
Garp didn't even feel that slash, but the fact that Morgan was able to draw blood from a man who trained his Haki to an extreme meant Armament Haki wasn't something that could be used all the time.
That's why Luffy would run out of Haki by using Armament Haki in Gear Fourth.
So, the difference between Observation Haki and Armament Haki was how much stamina his Willpower was going to consume.
That difference could be the key to unlocking Armament Haki without going through a life-and-death battle.
But without guidance and just a manual, it wasn't going to be easy to find that key.
Fortunately, Tyler wasn't in a hurry.
The ship sailed towards Totato Island while he continued training on the deck.
A day passed, and they finally reached the shores of Totato Island. When he got closer, Tyler's eyes shrank immediately.
He sensed nearly hundreds of people stockpiled in one place. But there wasn't a lot of blood smell, which meant it wasn't a place for Organ Trafficking.
Just when his ship moved closer to the shore, several individuals holding bazookas in their hands approached him.
"Stop right there! This island is under the protection of the Marine Branch G-77. You must leave. Or else, we will shoot."
A tall man holding a large microphone spoke through it.
Just when Tyler was about to unsheathe his sword, Frank spoke.
"Captain, let me handle this!"
"And me!"
Adam added as he stood next to Tyler. Both of them jumped towards the island.
Seeing this, the man holding the microphone shouted.
"Attack, blast them!"
Those holding bazookas and guns started shooting rapidly. But while in mid-air, Frank and Adam instantly used Iron.
[Iron]
Their bodies gained the durability of real iron as they tanked those attacks.
Bang! Bang! Bang! Boom! Boom!
The explosions of the bazooka engulfed the air.
"Hehe! Now you understand our threat! Shoot that ship!"
The tall man smiled smugly and shouted.
But one of his men started shaking in fear. His eyes widened, and the veins around his forehead popped out.
"Sssss….sirr.rrrr That's Tyler the Destroyer!"
He pointed his finger at Tyler and shouted on top of his lungs.
There was a deep silence in the air. The black dust from the explosion slowly faded.
Adam and Frank were still in mid-air, kicking the air. Frank had burnt marks on his collar and clothes. He also had a few dark spots around his ears.
"Hehehe! Your mastery over Iron is quite weak, Frank."
Adam burst into laughter when he saw Frank's situation.
Frank clicked his tongue and instantly disappeared. He appeared in front of the tall man and said.
"You were laughing just now, weren't you?"
The man hadn't even overcome the shock of seeing Tyler when he saw Frank standing in front of him.
He tried to talk to Frank, but before the words even left his mouth, Frank moved.
His rapier swung like never before, at speed, untraceable to the naked eye.
In an instant, that man was left with nearly a thousand cuts.
"Ahhhhhhh!"
As the pain finally hit him, the man screamed like a pig before the rapier pierced through his throat.
"They are gonna kill us! Attack them!"
One of the soldiers saw the tragic fate of his leader and roared. But instead of running towards Frank, he ran away.
The other soldiers, inspired by his words, raised their swords and rushed towards Frank.
Before Frank could even make a move, a figure suddenly appeared above him, and the hammer fell.
Bang!
The first wave was crushed under the force of his hammer. Adam didn't stop there. He held his hammer tightly and spun.
Bang! Bang! Bang! Bang!
The next wave was crushed by the spinning hammer.
"Hey, don't take my kills!"
Frank and Adam were literally treating this as a game, running towards their opponent, swinging a rapier and a hammer.
In less than five minutes, nearly two hundred people fell before them as two of them stood between these corpses.
Finally, Tyler landed on the island.
He asked Robin to stay behind just in case someone was hiding somewhere.
He didn't care about the belongings inside the ship, but he was afraid someone would harm Miya while she was unconscious.
"They are keeping all of the people there. Let's go!"
Tyler pointed his head towards a tall building, and three of them walked towards it.
"Come to think of it, are some of them hiding in this building? Our battle was quite loud."
--------------------
Check out the link in my description to read thirty chapters in advance