One Piece : Rise of Thunder King

You can read the advance chapters here : patreon.com/Vigilante04

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New World, Merk Island

Merk Island is a small and ordinary island under Whitebeard's territory. Since it has no special resources, no one lives here. However, ships from the Whitebeard Pirates sometimes dock at the island to make repairs and resupply.

Right now, a ship carrying both the Spade Pirates' Jolly Roger—a flag with a spade design—and Whitebeard's flag is docked here. This ship is called the Ace of Spades, the vessel of Portgas D. Ace.

On the beach, Ace's crew is enjoying a lively banquet. They're eating, drinking, and laughing, clearly having a great time.

Meanwhile, at the center of the island, Ace is with Luffy and the Straw Hat Pirates. They are here for a specific purpose: to train in Haki, focusing on Observation and Armament Haki.

At this point in their journey, none of Luffy's crew has mastered Haki, except for having witnessed it during battles. To help them, Ace has brought them to this island to teach them.

If this were the timeline of the original story, Ace would only have basic proficiency in Conqueror's Haki and Armament Haki. However, because of Arthur's influence and encouragement, Ace started training earlier and has become more skilled in Haki—especially Armament Haki, which the Straw Hats need the most right now.

Standing before Luffy and his crew, Ace removed his hat and began explaining seriously.

"In the New World, anyone who is strong must know how to use Haki!" he said.

"Haki is the only ability that doesn't come from a Devil Fruit but can counter the powers of a Logia-type fruit!" Ace's expression grew serious as memories flashed through his mind.

He recalled how, before learning Armament Haki, a Vice Admiral with tough Haki had completely overpowered him in battle. Although Ace eventually learned Armament Haki through his natural talent and hard work, that experience humbled him and shattered the overconfidence he once had in his Logia Devil Fruit powers.

"It can even counter Devil Fruit powers, including Logia?! That's incredible!" Usopp and Chopper exclaimed, their eyes wide with amazement. To them, Logia users like Crocodile and Smoker had once seemed invincible.

While Robin already knew about Haki thanks to her vast knowledge, the rest of the crew was intrigued. Luffy, Zoro, Sanji, and even Franky paid close attention. These four, who were the main fighters of the crew, had noticed traces of Haki in previous battles but didn't fully understand it.

Ace continued, addressing the crew with a serious tone.

"There are three types of Haki, and together they are known as Conqueror's Haki!"

"First is Observation Haki, which lets you sense your opponent's presence and even predict their movements without relying on your usual senses like hearing or sight."

"Second is Armament Haki, which works like invisible armor. It can enhance your attacks and defense, bypass Devil Fruit powers, and even let you touch Logia users."

"The third, and rarest, is Conqueror's Haki, which only one in a million people can possess. This Haki can't be strengthened through training—it grows stronger as the user's willpower and inner strength grow."

Ace's voice grew firmer as he explained. "Conqueror's Haki allows its user to overpower the will of others. If the difference in strength or spirit is too great, it can knock people unconscious instantly!"

"The first two types of Haki can be improved with practice, but Conqueror's Haki is tied to your natural willpower and strength. It's said that those who possess it are destined to be leaders, people with the qualities of a king. Not everyone who becomes a king has Conqueror's Haki, but everyone with Conqueror's Haki has the potential to become a king."

Hearing this, the crew was filled with awe.

"Only one in a million people can have it? And those people are destined to be kings?"

The rarity of Conqueror's Haki, combined with its incredible power, left everyone deeply curious about what kind of people could wield it—and what it felt like to experience such a force.

"Mr. Ace, I've read about Conqueror's Haki in some books, but I've never seen it up close. Can you show it to us?" Robin, the most knowledgeable member of the Straw Hat Pirates, couldn't hide her curiosity and asked Ace.

"Yeah, Ace! Show us! We've seen something like it before, but we're not sure if it was Conqueror's Haki," Luffy added, nodding enthusiastically.

"Alright, I'll show you," Ace said with a nod, closing his eyes. "First, let me demonstrate Observation Haki. Luffy, attack me!"

"Oh!" Luffy shouted, then immediately leaped forward, throwing a punch straight at Ace.

Whoosh!

Ace didn't open his eyes but dodged the attack effortlessly, as if he could see it coming.

"Huh? He dodged it?" Luffy said in surprise, while the rest of the crew widened their eyes in shock.

Some of them, particularly Zoro, were skeptical at first. After all, once a fighter reaches a certain level of skill, they can sense their opponent's movements by sound or subtle cues. As a swordsman, Zoro was already capable of this to some extent.

But their doubts vanished as they watched Ace avoid every one of Luffy's attacks. The key difference was that Ace wasn't reacting after the attack started—he was moving before Luffy even threw a punch.

When they remembered Ace's earlier explanation of Observation Haki, they understood. This wasn't ordinary prediction based on sight or sound. It was Observation Haki, the ability to foresee an opponent's actions without relying on physical senses.

"Now, I'll show you Armament Haki," Ace said after finishing his demonstration of Observation Haki. His arms darkened, coated with a hard, shiny layer of Armament Haki.

"Huh? What's that?" Luffy asked, noticing the change.

Without a word, Ace struck Luffy on the head, bypassing his natural rubber defense.

"Ouch! That hurts!" Luffy yelled, clutching his head as a large lump formed.

"Wait a minute," Sanji said, exhaling a puff of smoke. "Luffy's body is rubber. How can he feel pain from a punch?"

"That's because of Armament Haki's ability to counter Devil Fruit powers," Ace explained. "Armament Haki can harden your body, making it as tough as metal. It can also enhance your attacks and bypass the defenses of Devil Fruit users."

He continued, "Beginners usually start with Armament Haki by learning to coat their attacks with it. Once you get more skilled, you can harden your body like this. That's the second stage. The third stage is called Ryou—or Flowing Sakura. It allows you to project your Haki into your opponent or surroundings, but I'm still learning that."

"What about Conqueror's Haki?" Zoro asked, his eyes gleaming with interest.

Ace smiled at Zoro and replied, "I have Conqueror's Haki too, but I'm not very skilled at using it yet."

"Show us, Ace!" Luffy urged with a confident grin. "My friends won't be knocked out by it!"

Ace hesitated for a moment. Conqueror's Haki was the least refined of his abilities, and he hadn't fully mastered controlling its range. However, after seeing Luffy's confident expression and sensing the resilience of the Straw Hat crew, Ace nodded.

"Alright, but don't say I didn't warn you," he said. Taking a deep breath, Ace added, "Here it comes."

Everyone braced themselves, watching Ace intently.

Boom!

A powerful, overwhelming aura burst from Ace, spreading across the area like a tidal wave. It was intense but brief, as Ace quickly withdrew the Haki after releasing it.

Luffy, who also had the potential for Conqueror's Haki, stood unfazed. However, the rest of the crew froze momentarily. They felt their breath catch, and a heavy pressure weighed on them. Some of their faces turned pale, and they stared at Ace in awe.

The sheer force of Ace's Conqueror's Haki left no doubt in their minds. This was the power of a king—the ability to dominate others with willpower alone.

The inviolable will and overwhelming momentum of Conqueror's Haki left a deep impression on everyone present.

Fortunately, the Straw Hat crew had strong spirits. While none of them possessed Conqueror's Haki, they didn't succumb to unconsciousness. Still, Usopp and Chopper looked visibly shaken—faces pale, pupils slightly dilated, and beads of sweat forming on their foreheads.

"This is Conqueror's Haki? It's terrifying!" Usopp exclaimed, trembling slightly. "But... it doesn't seem all that useful in battle. If you're prepared for it, it shouldn't have much effect."

Zoro, observing calmly, nodded. "Yeah, it's intense, but it doesn't seem like a game-changer."

Sanji and Locke also agreed. While the experience was uncomfortable, it didn't leave a lasting impact on them.

Ace chuckled at their reactions, shaking his head. "That's because my Conqueror's Haki isn't particularly strong. In the New World, plenty of people have it, and compared to them, I'm only about mid-level."

"Mid-level?" Zoro and the others were taken aback.

"Yes, mid-level," Ace confirmed with a nod.

"Then who's the strongest?" Luffy asked, his curiosity piqued. The rest of the crew leaned in, equally intrigued.

Ace's expression turned serious as he answered. "The strongest Conqueror's Haki in the world belongs to someone you all know about. You've seen his deeds and heard his name. He's the ruler of the Angel Empire... King Arthur."

"That big brother?!" Luffy exclaimed, his mouth wide open as he recalled the past. "He's amazing! He helped me develop my Second and Third Gears!"

"What? You've met him?" Ace was stunned, clearly surprised.

"Yeah," Luffy nodded, then scratched his head as he tried to remember. "It was... um..."

"Alabasta," Sanji interjected with a sigh.

"Oh, yeah! In Alabasta!" Luffy's face lit up as he recalled the details. "We were fighting that guy—uh, what was his name again?"

"Crocodile," Locke said, rubbing his temple in exasperation.

"Right!" Luffy exclaimed, clapping his hands. "During the fight with Crocodile, that big brother was watching from the sidelines. He quietly gave me tips and helped me develop Second and Third Gear. He's a really good guy!"

Zoro, Sanji, and the others were astonished. They couldn't believe that the person recognized as the strongest Conqueror's Haki user in the world was someone they had already encountered—and someone who wasn't much older than them.

"I can't believe you've met him. Lucky for you, he didn't attack. If he had, you wouldn't have stood a chance," Ace said, his tone serious. "Every time Arthur is mentioned in the news, it's because he's done something world-shaking."

Ace paused, his eyes reflecting a mix of respect and determination. "Whether it was fighting Kaido one-on-one in the first half of the Grand Line or clashing with multiple world-class powerhouses at the Marine Base in the New World, every battle he's in becomes legendary."

Ace continued, "Since you've met him, let me use him as an example. His Conqueror's Haki is unmatched. The previous record-holder was Red-Haired Shanks, one of the Four Emperors—someone you know well, Luffy."

"Shanks?!" Luffy's face lit up with joy at the mention of his childhood hero.

"Yes," Ace said with a nod. "When Arthur first arrived in the New World, he had a Conqueror's Haki clash with Shanks. Rumor has it that Shanks' Haki was overwhelmed, and even Shanks himself didn't deny it.

Since then, Arthur has demonstrated his Haki many times, proving it to be the strongest. His Conqueror's Haki is so powerful that it can even affect the physical world—it has offensive capabilities."

Everyone was stunned into silence, trying to process the sheer magnitude of such power.

"But that's not all," Ace added. "Arthur's Observation Haki is equally terrifying. It's said he can perceive the inner thoughts of others and sense things from hundreds of kilometers away. His precision in battle is unmatched.

He can launch attacks over those same distances and still hit his target perfectly. No one else in the world can do that."

Ace's tone grew even more serious. "As for Armament Haki, his mastery is also incredible. Among the strongest Haki users, he's still near the top."

He paused, letting his words sink in before concluding, "Many believe that Arthur will one day be recognized as the strongest person in the world. Some already think he's earned the title. The only reason it's not official is because he hasn't fought my father yet."

Ace's voice softened, and a proud smile appeared on his face. "After all, my father—Whitebeard—is still the strongest."