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

Thunder Island.

An island constantly battered by thunder.

At first glance, the entire island was barren, devoid of vegetation and life, consisting only of rocks that had been tempered and refined over the years.

Deep purple lightning bolts continuously fell from the sky, becoming increasingly dense the closer one got to the center of the island.

In the heart of the island, lightning cascaded down like a waterfall, transforming the area into a blinding pool of lightning.

The proverbs of the Ark on the sea rise and fall with the waves.

As Roy and the others on the ship approached the island, they witnessed a shocking scene.

"This...this is Thunder Island?" Savi, Enel, Pea, Charon and the others swallowed hard.

Roy was secretly amazed by what he saw.

Roy's original plan was to head straight for Whitebeard's territory after leaving Fishman Island.

Let's see if we can catch up with the battle between the Roger Pirates and the Whitebeard Pirates, and continue to hone the strength of our crew.

But as Roy got closer to Thunder Isle, he sensed that the lightning power emanating from the island was constantly stimulating every cell in his body.

A tingling, slightly numb sensation seeped through the skin and into the body; each cell seemed to tremble slightly under this external stimulus, becoming more active.

Even the "forging" process of Armament Haki circulating within the body seemed to speed up slightly.

Although Tesoro can also perform lightning tempering, with his current control, he can only barely perform it for himself.

Even if he used his full strength, without Armament Haki, the effect on Roy, Barrett, and Hawkeye's physical bodies would be negligible.

Perhaps in the future, when he increases the power of his Devil Fruit ability by several levels and improves his control, he will be able to perform body tempering for others.

After all, the environment here could very well have been created by the Rumble-Rumble Fruit ability of a certain generation.

"Hahaha! That's awesome! Boss, can you feel it?"

"The lightning here... is filled with violent power! But it originates from the same source as my power, only it is more ancient and more powerful."

Tezoro opened his arms and continuously absorbed the free electron energy around him into his body.

"Not bad, the pressure is immense! Training in this godforsaken place will definitely have a far greater effect on tempering our domineering aura and physique than usual! Roy, should we stay here for a while?"

Barrett crossed his arms, his eyes filled with anticipation.

Roy looked at Mihawk. Although he didn't say anything, his constant stroking of the black sword Night seemed to be assessing whether he could cut through the lightning in the sky.

"Alright, let's go to the island!"

"However, the lightning on the island is too violent. Stella, Savi, Pea, Enel, Charon, the rest of you should find a suitable place to train on the outskirts."

"Barrett, Mihawk, the three of us will explore inwards to find a suitable area for our cultivation."

Seeing Tesoro waiting expectantly, Roy waved his hand.

"Do whatever you want!"

"But remember to act within your capabilities. The core of the lightning waterfall is definitely not something you can touch right now. Be careful."

Roy scanned everyone. "In the end, it's important for us to return life to our control as much as possible."

"Yes/Okay, boss!"

After activating the Ark's defensive mode, the group stepped onto the surface of Thunder Isle.

"Crack!"

The moment they touched the island, sparks flew from the ground beneath their feet. Everyone jolted, their fur standing on end.

One can imagine how violent the lightning was in the center of the island.

"Whoa!" Savi cried out, almost jumping up.

"The ground here is electrified!"

The pea looked wilted, suggesting that its plant nature meant it likely had little resistance to lightning. It stared longingly at Roy.

"Roy..."

Roy could only helplessly smooth his hair and give him an encouraging look.

Charon felt the tingling sensation coming from the soles of his feet, his expression serious.

"In this environment, I feel like all the water in my body is evaporating."

"Alright, the outer area is now yours. Remember not to push yourself. If you can't hold on, go back to the ship and rest. You can continue your training once you've recovered."

After giving their instructions, Roy, Barrett, and Mihawk exchanged a glance and began to venture deeper into the island.

As for Tezzolo, he disappeared long ago when Roy announced his arrival on the island.

As Roy and his companions ventured deeper, the concentration of free-floating ions in the air increased, and the frequency of lightning strikes from the sky also rose.

Deep purple lightning occasionally exploded around us, leaving sparks on the dark rocks.

Roy stopped in his tracks.

"I'll train here. If I go any deeper, even with my physical strength, I won't be able to withstand the lightning there without activating my Armament Haki."

Eagle Eye also pointed to the other side, where there was a relatively flat clearing, but the lightning strikes from the sky were even more frequent.

"That's a good place to practice swordsmanship."

As he spoke, he walked away alone, Black Blade Night already drawn, seemingly ready to challenge the thunder there.

Barrett, however, intended to continue forward, since his physique and the regenerative abilities of his mythical beast were indeed unmatched by Roy and Hawkeye.

The three of them each found a place to cultivate.

Roy sat down cross-legged immediately.

"Boom!"

A bolt of purple lightning, as thick as an arm, seemed to have found its target and struck straight down!

"Well!"

Intense numbness and tingling instantly spread throughout his body; the lightning here was far more violent than Tesoro's thunder.

Roy felt his muscles twitching and his bones groaning under the strain.

Every cell seemed to wail and shatter in the thunder, yet it quickly reorganized and regenerated under the immense vitality spurred by the return of life.

Zefa's "Internal Forging" was operating wildly, and with the rush of blood,

The violent lightning arcs that merged into his body seemed to become the best forging hammer, each flash making the flowing domineering energy more condensed and pure.

Walking on the edge of destruction and rebirth, Roy could clearly sense that both his physical strength and the quality of his Armament Haki were improving at an astonishing rate.

"It's three times faster than the usual tempering speed..."

This discovery gave Roy a great shock.

"It seems it's time to have Tesoro increase the power of his lightning..."

Not far away, Hawkeye was also undergoing the tempering of lightning, but he would occasionally raise the black sword Yoru in his hand.

He used his Observation Haki to its fullest extent to predict the trajectory of the falling lightning.

"Buzz—!"

The black blade sliced ​​through the air, directly striking the falling lightning. The collision of the blade and the lightning produced no loud noise; instead, it cleaved the lightning in two.

It disintegrated into chaotic arcs of electricity, continuing to temper his body.

"not enough."

Hawkeye's eyes were indifferent. He flipped his wrist, and the black blade danced in the night, creating a blur of afterimages as it met three, five, or even more bolts of lightning at the same time!

While harnessing the power of heaven and earth to temper their bodies, they also pursue precision, speed, and power in their strikes.

Seeking the supreme sword realm that can "cut through even lightning".

"Hahaha! Come on!"

Barrett laughed wildly, gathering all his Armament Haki into his fists, completely ignoring the lightning striking him.

He slammed his fists directly onto the boulder, producing muffled thuds, using the hardness of the rock to continuously hone his Armament Haki.