One Piece: The user of the Nen-Nen Fruit, who overturned the sea.

Seeing the chill rising in Barrett's eyes.

Roy remained calm and continued speaking in a low voice.

"You are strong now, but not strong enough. This world is vast, and the seas are teeming with powerful beings. With your current brute strength, how far can you go?"

"Are you now just a domesticated wild beast, ruling as king in the army of this tiny country?"

Roy's words instantly darkened Barrett's face. Although he was reluctant to admit it, he did crave challenges and enjoyed the feeling of becoming stronger, and he did feel a sense of constraint.

Seeing Barrett deep in thought, Roy extended the invitation again: "Join us, Barrett! This country is too small. With us, you'll see a wider world and encounter stronger opponents."

Roy's voice was seductive, and his mental energy probed out, subtly arousing Barrett's desire.

"We share the same goal: to become stronger. But the path I'm taking is more interesting than your solitary exploration, isn't it? Only by leaving this country can you witness even greater power, like... this."

Roy covered his palm with Armament Haki and waved it at Barrett.

"At least with us, I can provide the 'challenge' you need."

Barrett remained silent, staring at Roy's waving hand, his desire growing stronger. The campfire crackled, and the atmosphere around him became tense.

Tesoro and the others didn't dare to breathe, waiting for his answer.

Barrett ran his right hand over the medals on his chest for a long while before speaking in a stiff tone, though less implying an immediate intent to attack: "You think you can make me betray my country and become a pirate with you with just empty words!"

"Even if I want power, I can find it myself. Why should I join you? What gives me the right?!"

"Trouble. Although I can see that Barrett's heart has wavered, he still has feelings for this country!" Roy thought to himself.

Suddenly, Barrett's eyes fixed on Roy, his fighting spirit surging. He wanted to kill Roy, who had stirred his heart, and also hoped that Roy could give him a reason, which would also be an excuse for him.

"Defeat me, like... utterly defeat me right here!"

"Sigh! Do we still have to rely on strength to speak?" Roy sighed.

After telling Tesoro and the others to step back, Roy looked at Barrett, knowing that words had had their purpose, took a deep breath, and slowly activated his Observation Haki.

"As you wish."

---------------

Barrett dragged his exhausted body back to the camp, his battle with Roy ending in a draw.

Lying in bed, Barrett stared blankly at the ceiling, Roy's words echoing in his mind—"This country is too small."

"asshole!"

Barrett slammed his fist on the wooden board. "That damn Roy!"

------------

Campsite on the back mountain.

Tesoro was idly poking at the campfire.

"Boss, it's been three days already, is that guy not coming?"

"He will come."

Roy sat cross-legged on a boulder, surrounded by spiritual energy.

"How did you know?" Savi looked at Roy curiously.

How would I know? Can I say I've read the original work? He glared at the two people who had interrupted his cultivation.

"Get back to training now."

As soon as he finished speaking, Roy's lips curled up and he whispered, "He's here."

A rustling sound came from the forest a moment later, and Barrett's tall figure appeared at the edge of the camp. He was still wearing that green military uniform, but his eyes had softened considerably.

"Want to train?"

"Let's have another match."

Barrett did not answer and walked directly to the center of the field.

Neither side used their full strength in this battle. Roy was only using physical combat to fight Barrett in order to hone his fighting skills.

After the battle, Barrett did not leave immediately. For the next few hours, he quietly engaged in high-intensity training.

As dusk fell, Barrett prepared to leave. Before entering the woods, he stopped and, with his back to Roy, asked, "How long will you be staying here?"

"Who knows!" Roy replied casually.

Days passed like this. Barrett would occasionally come to the camp in the back mountains to fight Roy, and after the fight, he would train with Roy and his group.

Roy also taught Barrett the domineering training methods.

It must be said that Barrett's talent is indeed strong. After Roy used his mental power to let him experience the feeling of Haki twice, Barrett successfully guided Haki out and began to hone his Haki.

Roy didn't slack off either. While honing his Armament Haki, he also continued to develop his own abilities so that Tesoro and the others could grow up quickly.

Roy also focused his ability development on the manipulation of 'gravity'.

Initially, his core ability was the immense spiritual power he gained from his transmigration, which allowed him to awaken Observation Haki early on. Although he could perceive the thoughts of others, he could not interfere with them.

After consuming the Mind Fruit, one's mental strength is enhanced once again, and one can also materialize that mental strength.

Its initial application was also to manipulate the surrounding objects. Unlike Shiki's Float-Float Fruit, which grants the ability to make touched objects float, the user can manipulate them at will.

Roy's Nen-Nen Fruit ability is more direct. He can manipulate any object at will within the range of his Observation Haki, and he can also materialize his mental energy to defend against attacks and concentrate impacts, but it is not without its drawbacks.

The larger the range of control, the more things can be controlled, and the greater the difficulty of control. Furthermore, using the ability constantly depletes the user's physical and mental strength. (The Nen-Nen Fruit also consumes mental energy.)

Roy originally intended to use the Float-Float Fruit as a model, but he found that he couldn't do it. After realizing this, he understood that if he wanted to gain a foothold in this sea full of powerful people, he had to explore this power more deeply.

"The essence of gravity is the curvature of spacetime by mass... and perhaps one's mental power can simulate or even directly manipulate this curvature?"

Roy fell into deep thought.

He tried to concentrate his mental energy to the extreme, attempting to perceive and influence the object itself and a certain field in the space around it.

This is an extremely difficult process.

Initially, he could only make an extremely small deviation in the trajectory of a falling leaf.

But he was not discouraged. He unleashed his full Observation Haki, combined with his mental power, to meticulously perceive the most subtle connections between matter and space.

"No, it's not about pushing, it's about giving... or rather, changing the connection between it and the earth."

Roy had a flash of inspiration. He tried to use his mental power to create a temporary, reverse gravitational source under the target object, or to directly enhance the gravitational connection between the object and the earth.

Sweat dripped continuously from his forehead as his mental energy surged at high speed.

Finally, after countless failures, a stone in front of him suddenly sank down, and with a "crack," fine cracks appeared in the ground!

"We did it!" Roy shouted excitedly.

Although it is still very rough and consumes a lot of resources, the direction is right.