One Piece: Rising to Power as a Warlord of the Sea

"Really?"

"Of course! After all, why would I stop a man from pursuing his dreams at sea?" Natsu said with a slight smile, his lips curling up.

"Luffy, come here for a moment," Natsu called, and Luffy, curious, walked over. He had just heard that Natsu was going to teach Ace some incredible techniques.

"Smack!" Natsu playfully flicked Luffy on the forehead.

"Ah, that hurts! Natsu, why would you do that? I'm made of rubber, so why does it still hurt?"

Luffy covered his head, looking bewildered and annoyed at Natsu.

"Hahaha, that's just my way of showing love as your older brother, Luffy!"

Luffy: "(*￣rǒ￣)(ー_ー)!!" I can't believe you!

"Back to business, Ace. Just as you saw, I flicked Luffy on the head and caused him pain using what the people of the New World call Haki."

"Haki is a latent power within the human body, a force of presence, pressure, and intimidation. It's something everyone is born with, but many go through their lives without ever realizing it or, even if they know, are unable to use it. Ending life in haste, believing unwaveringly—this is a kind of strength."

As soon as he finished speaking, Natsu pulled out a black eye mask from his pocket and put it on, then said, "Ace, come! Attack me with all your might!"

"Are you sure?!" Ace replied, surprised.

"Absolutely! Just watch and learn!"

"Swish!"

Ace swung the water pipe in his hand down hard. At that moment, Natsu's body sank slightly, then he moved to the right, dodging the attack in advance while lightly opening his lips to say, "Ace, you're swinging the pipe to attack my head from the upper right, then moving to the lower left."

"Swish! Swish! Swish!"

Seeing Natsu dodge the attacks while predicting them made Ace increasingly frustrated. After twenty continuous swings, Ace finally stopped, his eyes filled with eagerness to learn.

Both Ace and Luffy looked at Natsu with eyes full of yearning to learn °˖✧︎◝︎(⁰▿︎⁰)◜︎✧︎˖°.

"Haki is divided into two types: Observation Haki and Armament Haki. The ability to sense a strong opponent's aura is known as Observation Haki. By enhancing this ability, you can sense the number and location of enemies outside your line of sight, and even foresee an opponent's attacks in advance. Just like what just happened, when Observation Haki is heightened to its extreme, it is said that one can see brief glimpses of future events."

"The other type is Armament Haki, which acts like an invisible, hard armor that enhances one's own attacks. Additionally, Armament Haki is the only way to deal with Devil Fruit users like Luffy. Without exploiting weaknesses, Armament Haki is the only method that can physically attack any Devil Fruit user, be it Zoan, Paramecia, or even Logia."

"Currently, the highest-ranking three admirals of the Navy Headquarters are all Logia Devil Fruit users. Without Armament Haki, they would become easy prey, utterly defenseless."

"Besides these two common types of Haki, there is also a rare, exceptional type called Conqueror's Haki. The top-tier warriors of the New World all possess this power, and even the Pirate King, Roger, had this ability."

As Natsu paused momentarily, Ace's expression turned somewhat angry and unwilling, his small fists clenched tightly, his nails digging into his flesh without him realizing it.

"Indeed, the Pirate King Roger also possessed Conqueror's Haki. I wonder if I will have it in the future."

Hearing Natsu mention Roger, Luffy's face lit up with excitement, mirroring how Bartolomeo reacted when he met Luffy later. This was the idol Luffy had always aspired to become!

"Hahaha, maybe you both have Conqueror's Haki as well!"

Natsu chuckled, responding to Luffy's mumbled thoughts.

"Now, let's begin our Haki lessons! First step, calm your mind and feel the power within your body…"

"Breathe in, breathe out, breathe in, breathe out~"

Understanding the power of Haki, Luffy and Ace began to learn with utmost seriousness. Especially upon realizing how many formidable monsters existed in the New World, both of them pushed themselves harder.

As for whether teaching Haki in advance would affect the subsequent plot development and create a butterfly effect, Natsu didn't care, because compared to these two, he was the greatest variable.

After all, what's the point of a time traveler who doesn't change the world? ¯(ツ)/¯

Time flew by like a fleeting shadow, and in the blink of an eye, Natsu had been there for half a month. Luffy and Ace, truly talented, had already mastered and could easily use Haki in such a short period.

After mastering Haki, Ace once again won against Luffy, delivering a "Fist of Love" on Luffy's head. Luffy immediately yelled, baring his teeth in pain.

"Damn it, Ace! Next time, I'll definitely defeat you!"

"Hmph! Luffy, you couldn't win against me before, and now that I've mastered Haki, there's no way I'm losing! Hahaha!"

The two brothers lay on the grass, bickering playfully, their happy laughter echoing throughout the forest.

"Sigh~"

"What's wrong, Luffy?"

Hearing Luffy sigh, Natsu asked, puzzled.

"It's a pity that Sabo isn't here. Otherwise…" ᵟຶᴖᵟຶ

"Don't be sad, Luffy. Maybe Sabo is still alive. After all, you guys didn't see the body, did you? Once you set sail and travel around the world, on your journey to become the Pirate King, you might just run into him." Natsu encouraged, though he didn't reveal anything about Sabo being in the Revolutionary Army. The meeting of the three brothers needed a better opportunity and timing.

"Hehe! I will definitely travel around the world, find the great treasure! I'm going to be the Pirate King! ๑(●´৺`●)۷"

Once the topic of the Pirate King came up, Luffy became extremely excited, doing a backflip off the ground, his face beaming as he looked at the endless sea, boldly declaring, just as the waves rolled in response to Luffy's grand words, the ocean surged wildly, with waves crashing one after another.

"Psh! Boring dream," Ace said with a complex look, curling his lips. He didn't quite understand what was so great about being the Pirate King.

"Hmph! ╭(╯^╰)╮ The Pirate King is the freest man in the world! He's so cool, okay?" Luffy pouted, refusing to back down.

"Hahahaha!"

Natsu burst into laughter at the familiar scene before him.

Three minutes later, Luffy lay on the ground, sound asleep, bubbles of snot stretching as he breathed.

"Ace, don't mind other people's opinions about the Pirate King! Maybe he's not as evil as people say. Once you set sail, experience it with your heart, and perhaps many of your knots will untie as you go along."

On the hillside, with a gentle breeze brushing past, Natsu stood side by side with Ace. During their time together, Luffy inadvertently revealed Ace's identity. Although Natsu had already known, he still pretended to be surprised.

Now, the two engaged in a simple conversation about the Pirate King Roger.

Opinions on Roger were mixed; his one sentence initiated the Great Age of Pirates, prompting countless young people to become pirates in pursuit of the great treasure, entering the New World, and along the way, causing chaos and destruction, leaving many innocent people suffering. This was the downside.

On the flip side, Roger achieved unprecedented accomplishments, reaching the final island, Laugh Tale, acquiring the great treasure, and learning about the World Government's efforts to cover up the void century. The arrival of the Great Age of Pirates ushered in a new era, empowering a group of young people to rise up against the oppressive Celestial Dragons, laying a significant foundation for peace and equality in the new world. This was the upside.

Thus, Natsu didn't make a simplistic judgment. Instead, he explained his views from an omniscient perspective, leaving Ace's decision up to him—something others could not interfere with.