The Caged Bird Seal.
Tanaka obtained that technique from Hiashi after exterminating the main house.
Now, he was the only person across both the Naruto and One Piece worlds who could both use and break the Caged Bird.
He had a deep understanding of the power system in the One Piece world.
No matter how bizarre a Devil Fruit ability might be, as long as one possessed sufficiently strong Haki, they could resist its effects.
For example, Kaido and Big Mom were not only immune to the cutting power of the Op-Op Fruit, but even the spatial displacement effects of the fruit had no impact on them.
Similarly, Law was able to resist Doc Q's Sick-Sick Fruit ability using Armament Haki.
This meant that if Tanaka were to rely solely on the Op-Op Fruit to completely control Kalifa, Jabra, and Blueno, it might not be impossible, but there would be a significant chance of them breaking free. But the advantage of the Caged Bird was that it was unknown in the One Piece world. And people generally feared what they didn't know more than familiar threats.
Thus, from the moment he decided to bring CP9 under his command, he had already crafted a specialized binding technique tailored for them.
"W-What is this...?"
Kalifa could distinctly feel an unusual sensation spreading from her head.
"The Caged Bird. There was once a person who told me this: Simply engraving the Caged Bird isn't enough. Only by making the person experience its power firsthand can loyalty and fear be engraved into their mind together."
Tanaka withdrew his hand from Kalifa's head.
He did not immediately activate the Caged Bird. Instead, he posed a question to her:
"I will give you a choice."
"Die here. Or experience the power of the curse seal once."
He spoke each word clearly and deliberately.
When Tanaka first obtained the Caged Bird technique from Hiashi, he was initially amazed by the ingenuity of the Hyūga clan members who created it.
But then, he realized just how utterly foolish the main house had been.
The Caged Bird, even from a broader perspective beyond Konoha, was one of the most powerful techniques for controlling people.
Yet, the Hyūga clan used it on their own kin?
Foolish. It should have been used on people outside the Hyūga clan.
Especially on enemies.
In his view, engraving this curse seal on the heads of his enemies was the correct way to use it.
However, the main house was just like Konoha's Hokage elders.
When dealing with their own people, they were highly skilled, intelligent, and ruthless. But when faced with outsiders, they immediately became weak and cowardly.
"I choose to be loyal to you," Kalifa answered almost without hesitation.
At this point, how could she turn back?
If she chose death now, then all her previous submission to Tanaka would have been meaningless.
Moreover, as a member of CP9, she had confidence in her ability to endure pain.
Being struck by lightning, burned by fire, or cut into pieces—these things could only destroy her body, not break her will.
"I understand."
Hearing this, Tanaka formed a hand seal with his right hand.
The once-confident Kalifa's expression instantly changed.
The seductive smile that had just graced her lips vanished in an instant, replaced by a look of sheer horror—her mouth gaping open so wide that an egg could fit inside.
Immediately afterward, she suddenly slammed her forehead into the sand with a loud "thud."
As if pressing her head into the ground was the only way to lessen the pain, to hide her humiliation, and to suppress her impending screams.
But—
"AAAHHH!!"
Within three seconds, Kalifa clutched her head in agony.
Even with her face buried in the sand, her bone-chilling screams pierced through, reaching Tanaka's ears.
Seeing this, his face remained completely unfazed.
This was the power of the Caged Bird.
A technique that had once driven countless branch house members to despair.
He had personally experienced it once himself.
Kalifa only lasted three seconds.
He had endured it for a full thirty seconds.
If it weren't for Hizashi pleading on his behalf, it wouldn't have been just 30 seconds—it would have been 60.
"Ahh! It hurts! Stop, stop, make it stop!"
What was CP9?
It was an elite unit selected by the World Government from countless children, handpicking those with the highest potential and meticulously training them step by step.
They mastered the Rokushiki and various espionage skills.
Their will was unshakable, their bodies were incredibly strong.
That was CP9.
But now, under the torment of the Caged Bird, she lasted 45 seconds before regretting her decision. However, as her gaze briefly swept over the unconscious Jabra and Blueno, she gritted her teeth and forced herself to endure, remembering that Haki could potentially break the seal's power.
What could make CP9 submit?
Not some twisted form of "Dark Justice," but the lives of their fellow CP9 members.
The World Government had long allowed CP9 members to form emotional bonds on purpose.
After all, emotionless killing machines were the easiest to lose control of.
But CP9, bound by a web of irreplaceable emotions, were actually easier to manipulate.
60 seconds.
To most, it might seem fleeting, but to her, those 60 seconds felt longer than the 15 years she had lived.
By the time Tanaka released the hand seal and withdrew his palm, she was drenched in cold sweat.
Her clothes and pants were soaked through, as if she had just been pulled out of the ocean.
As the pain gradually receded from her brain and eyes, her body went limp, collapsing onto the sand.
Her lips parted slightly as she gasped for breath.
"Let me tell you something."
"No matter where you run, whether at the beginning of the Grand Line or at its very end, as long as I wish it, I can activate the curse seal on your head at any time."
"Don't even think about finding a way to remove it."
"This is not a Devil Fruit ability, so Haki is useless against it."
Tanaka took in Kalifa's wretched state without the slightest hint of sympathy—let alone pity.
He hadn't forgotten that this woman had come here to kill him.
If he hadn't possessed his current strength, he wouldn't have even had the chance to beg for his life.
He would have been beaten half to death by CP9, handed over to the World Government, and suffered a fate far more despairing and agonizing than simply being branded with the Caged Bird.
A CP9 agent, drenched in blood, harboring cruel intentions.
It didn't matter if she was a woman.
It didn't matter if she was more beautiful.
It didn't matter if she had a great figure.
As long as she harbored ill will toward him, he wouldn't feel the slightest bit of mercy.
He would respond with the utmost cruelty.
Just like now.
Die here. Or live and be marked with the Caged Bird.
No. Even branding her with the seal wasn't enough.
Tanaka hadn't forgotten—he had once used the Op-Op Fruit to break free from the Caged Bird himself.
In the world of One Piece, there were countless Devil Fruits.
And among them, there must be more than one that could break the Caged Bird.