After working together for some time, Aki began to understand Kenji's true nature.
The fifth field mission for the partners, Kenji and Aki, was hunting a high-level Spider Devil in a dense forest in Chiba.
The fight was intense. Aki attacked aggressively with his katana, but he was affected by the Spider Devil's venom, slowing his movements unnaturally.
Kenji: (A composed voice laced with amusement) "Aki. Wow... this slow reaction time. Are you getting old?"
Aki: "Shut up! I don't need orders from you!"
Aki attempted one final slash, but the Spider Devil countered with a massive claw. Kenji didn't have time to draw up a quantum diagram; he used Mūkagen (Infinity) in its fastest form.
In that instant, the distance between the Devil's claw and Aki's body was stretched into infinity.
Kenji: (Chuckles slightly) "Alright! Movement stopped, you slow Devil Hunter. Now's your chance!"
Aki seized the moment the claw's movement was halted to slash the Spider Devil's head cleanly off. The Devil instantly became a corpse.
When the mission ended, Aki offered no thanks. Kenji merely stood, arms crossed, offering an irritatingly smug smile. Aki was deeply displeased at having to rely on this kid's "strange power."
The Curse Devil Contract
Two days later, Makima summoned Aki and Kenji. She spoke of Aki's need to gain more power for the sake of his vengeance.
Makima: "Aki-kun, your hatred is a powerful driving force, but your body cannot keep up. You require a power that can compensate for the time you don't have."
Makima: (Looking at Aki) I have an option for you, Aki-kun. Do you want power? But you will have something to lose in exchange.
Aki: Of course. I need power.
Makima: "I've prepared a suitable entity. The Curse Devil. Follow me if you wish to form a contract with it."
In a darkened room, the Curse Devil was confined. Aki walked closer to the Devil, his eyes filled with terrifying resolve.
"You... human filled with hatred... I will grant you power... the ability to slowly kill those you curse," the Devil's voice echoed in the room.
Aki: "What is the condition?"
"The condition is your lifespan. Every time you invoke my power through these black nails... I will trade it for a duration of your lifespan. It is not an upfront payment, but a payment upon every use. The amount I take is not fixed... it could be months, it could be years... depending on the severity of the victim you wish to slay and the weakness you hold due to your hatred."
Aki knew that the contract with the Curse Devil was dangerous because the Devil did not specify the exact amount of lifespan. But he chose to proceed without hesitation for his revenge.
Aki: "I accept the offer." But I request to utilize the contract through a nail sword instead.
I accept your contract. (The Curse Devil's voice)
Aki left the room with a small, fresh wound on his cheek and the nail sword. The contract was made, and it came with the terrifying uncertainty of shortening his remaining lifespan with every use of the power.
After returning from making the contract, Aki went to report his agreement with the Devil to Makima.
At Public Safety, Makima's Office
Makima: "Aki-kun, I see your determination, but losing your lifespan to the Curse Devil means you don't have much time left."
Aki: (Steadfast expression) "I don't care. I need the power to deal with the Gun Devil as quickly as possible."
Kishibe: (Standing in the corner, wearing the same coat and sipping liquor) "Hmph... Those who rush always die first. Watch your bones, kid."
Aki ignored Kishibe's warning and made the contract without hesitation, exchanging power for the ability to kill. The contract was finalized. Aki left the room to return to the apartment with terrifying determination and the nail sword slung across his back. Every use came with a cost in years.
The 'Selfish' Promise
After returning to the apartment, Aki immediately collapsed into bed from exhaustion. Kenji remained seated on the sofa, not having closed his eyes for a single second.
Kenji: (Walking closer to Aki) "Hey, Aki."
Aki: (Groggy voice) "I told you to be quiet..."
Kenji: I overheard you talking to Miss Makima about your contract with the Curse Devil. Is it true that every time you use that power, you have to trade a portion of your lifespan?
Aki: So what?
Kenji did not reply but wore a look of complete boredom.
Kenji: "How about this, Aki? If I protect you on the battlefield, you can take your time with your vengeance without worrying about your lifespan. I'll help you."
Kenji: "And I won't charge extra! I'm doing this because... I don't want a partner who dies this quickly. It's boring, and if you die before you get your revenge..."
Aki clenched his fists, unable to deny the terrifying truth spoken by the emotionless Kenji. He knew this was his only chance.
Aki: (Trying to calm himself) "Why... would you do that for me?"
Kenji: (With a mocking smile) "Because Miss Makima ordered me to be your partner, old man, and having a partner die before achieving their revenge will drastically reduce my personal happiness. Understand? I'm doing this purely for myself."