One Piece:The Fruit of Evolution

Ron didn't spend much time at Naval Headquarters. After all, he still had the Marine Base to guard, and the G8 Fortress had a unique geographical position. Without a strong defender, it could easily fall prey to pirates. Moreover, the deployment of the fleet would take nearly a month, and he didn't have time to wait that long at the Headquarters.

Leaving Marineford, Ron headed back to G8 Fortress. Before leaving, he didn't forget to propose to Vice Admiral Tsuru, but as expected, she flatly rejected him.

"When you become an Admiral of the Headquarters, I'll consider it," she said. Whether this was meant as encouragement or to dissuade him, Ron wasn't one to back down.

"Admiral? That's no big deal," he mused. With his strength, if luck was on his side, he would likely become an Admiral within three years. Once Marshal Kong stepped down, the position would likely be his. As for Sengoku? He wasn't a threat.

"With me around, do you really think you're going to be the next Marshal?" Ron thought smugly. 

Returning to the fortress, he pondered his next move. "I've gained the power of evolution again—where should I use it this time?"

Battling was the fastest way to grow stronger. His fight with Byrnndi World had triggered the evolution of his Armament Haki, and after killing him, the power of "Crimson Cry" had strengthened his physique further. 

After all, Byrnndi World wasn't just any enemy; he was an Admiral-level powerhouse. There were only a handful of such warriors in the entire Grand Line. Reaching this level meant having survived countless battles, each more brutal than the last. Naturally, defeating such an opponent granted Ron the chance to evolve his power again.

"Weapons and battleships have already evolved, but my body hasn't fully transformed yet," Ron thought, deciding to focus the power of evolution on his skin. 

The skin represents defense, and if it could evolve to be as hard as steel—combined with Iron Body and Armament Haki—his defensive capabilities would skyrocket. While he might not yet be able to kill a peak Admiral-level powerhouse in a head-on fight, being able to survive their attacks was enough.

"If I can't be killed, I'm invincible."

Ron reflected on Kaido, one of the future Four Emperors. Despite being captured by the Marines multiple times, they could never kill him, primarily because of his thick skin and long stamina. Marine Vice Admirals couldn't even scratch him, and while Admiral-level powerhouses could injure him, they couldn't finish him off.

Even Sengoku was frustrated whenever he faced Kaido, who constantly taunted him with his apparent invincibility.

However, Ron wasn't convinced by the title "strongest creature on land, sea, and air."

"Kaido can't be killed? He clearly hasn't faced Garp's fists. Otherwise, his dragon scales would have been crushed already," Ron thought confidently.

No one was truly invincible in this world; every creature had a weakness. Even the strongest Devil Fruits had vulnerabilities—it was just a matter of discovering them.

As far as Ron knew, Armament Haki trained to the highest level of internal destruction could theoretically kill Kaido. But among the Marines, only one person had reached that level—Garp. Even Haki specialists like Zephyr, who had focused entirely on it, only reached the third stage: Haki release. The fourth stage, internal destruction, felt as elusive as Roger's ability to hear the voice of all things or Katakuri's future sight. Reaching that level required not just practice, but innate talent.

Ron activated the power of evolution, feeling his skin harden like cowhide.

"It feels similar to using Iron Body," he observed, tapping his skin, which now felt as solid as iron. Combined with Armament Haki and Iron Body, this would allow him to endure Admiral-level attacks. While he might be injured, he wouldn't be killed.

Moreover, the evolved skin had an added benefit: it could grow stronger by being hit. The tougher the attack, the more resilient his skin would become. 

"Getting stronger by being beaten up—sounds simple, but it's not really my style," Ron thought with a hint of irony. As a Vice Admiral and a master swordsman, the idea of needing to get hit to grow stronger didn't quite fit his dignified image. People might even mistake him for someone who enjoyed pain.

[Don't worry, I won't make him do this. He will not ask anyone to beat him, nor will he appear to be trying to get his enemies to beat him. 

I'm writing this because I've noticed that in several stories about people with this power asking to be beaten, there is speculation that they are people who enjoy pain. This makes me throw up.

 No, I won't do that in my story.

 Stay tuned for how his skin will develop.]

Leaving Marineford aboard his warship, Ron set a course for G8 Fortress. Along the way, a pirate ship appeared on the horizon. Ron glanced at its flag, vaguely recognizing it but unable to recall the exact pirate group. If memory served him right, the captain had a bounty of over 100 million bellys.

Before the era of great pirates began, a bounty over 50 million was already considered high, making waves in the first half of the Grand Line. A pirate with a 100-million bounty was a force to be reckoned with. Even Byrnndi World, an Admiral-level fighter, had a bounty of only a bit over 200 million, demonstrating the weight of a Marine-issued bounty.

Once the era of great pirates began and inflation set in, bounties would skyrocket into the billions. But for now, a pirate with a 100-million bounty was as strong as a Rear Admiral, while those with bounties over 200 million were comparable to Vice Admirals. The 300-million mark was the threshold for the most powerful pirates, with those over 400 million either being Admiral-level or on the verge of it.

Normally, an Admiral-level fighter would have a bounty of 400 to 500 million bellys. Byrnndi World's relatively low bounty wasn't a reflection of his strength but rather a consequence of being a new player compared to the remnants of the Rocks Pirates, like Whitebeard. Though powerful, he hadn't yet committed any acts that seriously threatened the World Government, so his bounty remained modest.

In reality, Byrnndi World's bounty should have been in the 400-500 million range, especially given the era when bounties over 400 million were reserved for the world's elite.

Even the Golden Lion's bounty was only 600 million berries.

Roger's inflated bounty, aside from the World Government's likely exaggeration, was due to his attempts to uncover the hundred-year void in history—a period the World Government desperately wanted to keep hidden. In their eyes, Roger's pursuit of that knowledge was more dangerous than the Rocks Pirates ever were.

Naturally, the World Government set his bounty at a staggering level, knowing full well no one could collect it.

[Hey everyone, my opinion on why the Marines can't execute Kaido is that he can escape, whether by flying or by using his Fish-Fish Fruit to move in the sea.

They can't kill him because even if they defeat him in battle and he's seriously injured, they can put Sea Stone on him, but once he recovers, he can break free using his Conqueror's Haki and escape.

As for the idea of feeding him a second Devil Fruit, causing the two fruits to clash inside him, I also have a theory about this: a strong Devil Fruit can overpower a weaker one. So, the World Government wouldn't waste a powerful Mythical Zoan fruit just to kill Kaido when they could use it to create someone with his abilities. This is just my personal opinion,

though—maybe Oda simply wanted to make Kaido seem more terrifying without needing to explain all these details]