The underground chamber trembled as the last of the Straw Hats reassembled. Dust and steam curled from vents in the floor, casting long shadows across the metal walls. They had faced isolation, trials, and illusions—but now, they stood as one.
"Looks like we made it back," Zoro said, sliding Wado Ichimonji back into its sheath.
"Of course we did! I was never worried!" Usopp declared with a shaky laugh, visibly sweating.
Nami scanned the area. "Where's Kael? He was watching everything, wasn't he?"
Before Robin could respond, a platform began lowering from the high ceiling with a screech of ancient gears. The group turned as the figure cloaked in black robes descended with slow, deliberate steps.
He pulled back his hood to reveal a stern, weathered face—eyes sharp, scarred across one side.
"Commander Riven," Robin murmured. "He was part of the World Government's Weapon Division. Disappeared after Enies Lobby."
Franky narrowed his eyes. "Now I know why this whole place gave me the creeps. This is a lab. And not the fun kind."
Riven raised a remote and spoke. "Welcome, pirates. You've survived my maze. And now, you'll witness the truth: the activation of the government's final weapon."
With a hiss of steam, the wall behind him opened, not to reveal a machine—but Kael.
He stepped forward, stiffly, as if pulled by strings. His expression was blank, unreadable.
"Behold, Project Hellix," Riven announced. "The human weapon. Born of science, engineered through pain. Your observer was never independent. He is mine."
Luffy scratched his head. "Wait. Kael's the weapon?"
"Figures," Zoro muttered. "I knew something was off."
Sanji lit a cigarette. "So he's been spying on us all this time?"
Franky clenched his fists. "You turned a human into a weapon? That's lower than scrap."
Kael's fingers twitched. Red lines pulsed under his skin—veins of energy coursing from a metallic core embedded in his back. His face was pale, eyes distant.
"You're not a monster," Chopper said softly, but uncertain.
"Kael! It's me! Usopp! But... were you lying this whole time?" Usopp said, voice wavering.
Kael looked at them, eyes clouded. He stepped forward slowly. The Straw Hats tensed.
"You want to see what I am?" Kael said, voice low. "Then let's find out if you're really worth your names."
Without warning, he lunged.
Zoro blocked the first strike with his blade. "So this is what you want, huh?"
Kael's movements were lightning-fast. He ducked under Zoro's counter and launched an elbow at Sanji, who spun midair to deflect it with a flaming kick.
Robin tried to restrain him with blooming limbs. "Clutch!" she cried, but Kael contorted his body in midair, avoiding her grasp with a strange flexibility.
Kael's mind spun. "Don't lose who you are, Kael. No matter what they do to you." Noel's voice echoed in the back of his mind.
The fight escalated. Blow for blow, Kael tested them all, pushing them to their limits. Each time he traded hits, Noel's voice returned, echoing through his fractured mind.
Eventually, a blow from Sanji's Diable Jambe struck Kael in the ribs, sending him skidding across the floor.
He coughed, wiped blood from his mouth, and looked up—finally, clearly.
"You... you all fight like you care about something real," he said.
Zoro lowered his sword slightly. "Of course we do."
Kael's breath was ragged. "I needed to see it with my own eyes. That it wasn't all a fantasy. That your loyalty... your freedom... it's real."
His knees buckled. He dropped to them, exhausted.
"I'm done," he whispered. "I can't fight anymore."
Luffy stepped forward, fists lowering. "Then stop fighting. Stand up as yourself."
Kael looked at him—peace beginning to return to his eyes.
Then—
A sharp BEEP echoed through the chamber.
Riven, high above, clicked a button on the remote. "You fool. You thought choice was yours?"
Kael screamed. Red veins flared across his skin. His body twitched violently, jerking upright as if yanked by invisible strings.
At the center of his back, hidden until now, a small panel hissed open to reveal the true Hellix Core—pulsing with red and blue light. It had been dormant, buried deep. Until now.
"Failsafe override engaged," Riven declared. "You belong to me again."
Kael turned toward them, red light flooding his pupils. His mouth twitched, struggling to speak, but his body moved on its own.
"Kill them," Riven ordered.
Kael lunged—but this time, something changed.
Mid-strike, Kael's eyes flickered. His hand stopped an inch from Luffy's chest, shaking.
Luffy didn't flinch. "You're still in there."
Kael's whole body trembled. His teeth clenched. Sparks flew from the exposed Hellix Core.
"You're not a puppet. You're my brother, Kael." Noel's voice returned, loud and clear.
With a roar, Kael grabbed his own back—fingers clawing at the exposed core—and tried to resist. His body shook violently. Energy crackled from the device.
"You can't override me forever," Kael gritted out, blood dripping from his mouth.
The Hellix Core surged with power, flooding Kael's limbs with forced commands. He screamed, body arching. But even as the override deepened, his fingers tore at the housing.
Suddenly, a sharp jolt of blue light burst from within the core—and Kael's body froze.
Riven's eyes widened. "What—?!"
Kael, bleeding and shaking, looked up at the Straw Hats. "Run. Please. I can't... hold it much longer."
The Straw Hats hesitated.
Robin called out, "We're not leaving you!"
But Kael roared, turning his head with monstrous effort toward Riven. "This ends with me."
He slammed a fist into his own chest, cracking the outer shell of the core.
The red glow pulsed—and then erupted.
A shockwave burst outward from Kael's body, tossing debris and shaking the walls. His body lifted from the ground, suspended by a growing sphere of energy that shone brighter than before.
Kael's eyes burned red, then blue—then both. The Hellix Core had activated in full, no longer simply under Riven's control. It was something more.
Luffy squinted. "Whoa... what is that?"
Robin shielded her eyes. "The core—it's not just control. It's enhancement... maybe something worse."
Kael roared as wings of glowing energy burst from his back. The floor cracked beneath him. He screamed—not in pain, but in loss. His expression was gone, hollow.
Then, his body went limp.
He crashed into the ground unconscious.
The room fell silent for a moment. But then—
The Hellix Core pulsed. Slowly, the veins of red reignited. Kael's body twitched.
A mechanical voice echoed from the core itself: "Unit online. Directive: annihilate."
Kael's eyes snapped open, glowing fully red. But they weren't his.
He stood—without a word, without a will.
Controlled entirely by the core.
Riven grinned manically. "Yes... finally. The Hellix Core has chosen itself."
Sirens blared. Robin turned. "He's activating a total collapse!"
Franky shouted, "We have minutes! Grab him—something's wrong!"
Luffy clenched his fists. "That's not Kael anymore."
The Straw Hats stared in horror as Kael, now possessed by the Hellix Core, stepped toward them with unrelenting precision.