One Piece: I will become stronger by checking in

After a while, the black flames surrounding Kai slowly faded. His blood-red hair began to revert to black, and the color in his pupils shifted back to a golden hue, the fiery glow returning to his eyes.

Feeling the bloodlust gradually subside within him, a small smile tugged at Kai's lips.

"Damn, Geluo, you're tough to control," he muttered to himself, referencing his inner demon.

Fortunately, his will was strong, tempered by years of watching countless action heroes and enduring hardships in his past life. Without that mental strength, it would have been impossible to hold himself together through this chaos.

Now that clarity had returned, Kai shifted his attention.

"System, care to explain why there's a glitch in this form?"

The system responded with a nervous tone, [You know, I'm just a system. Bugs are kind of... normal, right?]

Kai nearly exploded with frustration, "Are you kidding me?! How do you explain the massive drawbacks of the demonic form of my Mythical Zoan fruit?"

[The host's fruit is based on the form of the Monkey King. Naturally, like the Great Sage, you've inherited both his power and his darker nature.]

Kai interrupted, "So you gave me the dark side of the Great Sage too? Figures."

[... Host, you're really sharp.]

Kai rolled his eyes. "Anyway, you've made a huge mistake. This demonic form has too many disadvantages. What if I lose control of my murderous intent and pick a fight with a Yonko?"

Pausing for dramatic effect, Kai smirked. "You owe me compensation."

The system hesitated, sensing the opportunity for negotiation, [What does the Host want in return?]

Kai grinned. Now came the fun part.

"I'm not asking for much. Just remove the downside of the demonic form—the uncontrollable murderous intent."

Kai had experienced firsthand the immense power of the demonic form. It enhanced all his abilities beyond belief, similar to Luffy's Gear 5 Nika form. If he could harness that power while fighting someone like Mihawk, he knew he wouldn't win, but he'd definitely last longer and push Mihawk even further.

However, the form's two major flaws held him back. The first was the enormous energy drain, which was tolerable. After all, every time Luffy went into Gear 5, he practically collapsed afterward. So Kai figured that extra energy consumption was normal.

The real problem was the murderous intent. In this form, Kai's desire to kill reached terrifying levels. The longer he stayed in it, the more overwhelming the bloodlust became. Sure, this time, the bloodlust had faded slowly since he didn't consciously activate the form. But what if he couldn't kill enough to suppress it next time?

Relying on slaughter to stabilize himself was hardly a sustainable strategy.

[Host's request detected. Processing...]

[Request analyzed. Rejected.]

[The core of the demonic form is its killing intent. Without it, the form loses its essence. However, the system can make the killing intent controllable. If you wish to erase it entirely, the form must also be erased. Do you wish to proceed?]

"Wait—what? No, don't erase it!"

Kai was momentarily startled, but quickly realized what the system had just offered.

Hold on—did it say controllable murderous intent?

This was huge! Having control over his bloodlust without being overwhelmed by it was a game-changer. Smiling, Kai immediately responded, "Then make the murderous intent controllable!"

As soon as he finished speaking, Kai felt a strange energy flow through his body. He closed his eyes, focusing on the sensation, as the system modified the murderous intent within him.

Meanwhile, Luffy, having noticed Kai's transformation earlier, began approaching him, eager to check if everything was alright. However, halfway there, Kai suddenly re-entered his demonic form, sending a shockwave of killing intent through the air.

Luffy instinctively stepped back, his eyes wide with alarm. The killing intent was so powerful that everyone around felt like they were standing in a battlefield filled with corpses. Usopp collapsed to the ground, his legs trembling with fear, while Zoro, even with his iron will, felt a flicker of unease.

They all stared at Kai with a new level of caution.

But Kai, on the other hand, felt amazing. The change had been completed, and he now fully controlled the murderous intent surging through him. He could direct it at his opponents, suppressing them with sheer mental and physical pressure.

Satisfied, Kai finally opened his eyes, only to see Luffy and the others standing as if they were ready to fight him.

"What are you all doing?" Kai asked, confused.

Luffy hesitated before nervously asking, "Are you... really Kai Vane?"

Kai's eyes narrowed in frustration. "Of course I am. Can't you tell?"

Luffy scratched his head. "But… Kai didn't have black hair or black clothes. And his eyes weren't red either. Plus, there's those black flames."

Kai sighed. Of course Luffy wouldn't understand a simple transformation.

"Can't a guy change his look every now and then?" he grumbled. But knowing it was pointless to argue with Luffy, Kai deactivated his demonic form. The black flames disappeared, and his hair and clothes returned to their usual colors. The only thing that didn't change were his golden eyes, which were now permanently part of his Blazing Eyes ability.

"Is this better?" Kai asked calmly, staring at Luffy.

Luffy blinked, then smiled wide. "Yep, much better! Welcome back, Kai!"

Kai couldn't help but chuckle. Though his power was dangerous, he finally felt in control. And that was all that mattered.

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

Power Stones would be appreciated if you like the story