Young man was restrained and strapped to the table in the middle of certain underground laboratory. Vials filled with different liquid and complicated machinery could be seen in the room.

Besides the table stood cloaked figure and one other person. He slowly approached the boy and looked at the marking covering his chest.

"First, let's get rid of this." He said.

He placed his hand on the markings and deactivated the Celestial Prison.

Sora's chakra became active again after restriction was removed. He struggled against the bindings, but it was meaningless. Mui didn't care for his wellbeing. No matter what price he had to pay, only thing that mattered was his goal.

He connected his chakra to Sora's and started syphoning boy's chakra towards the giant box placed other side of the room. Soon, chakra color that was drawn from Sora begun to change from blue to red. It became more dense, wild and chaotic. Sora thrashed even more fiercely from the pain, but Mui didn't pay any mind to it.

That was when, suddenly, he sensed that someone was approaching the laboratory. Next moment, something barged into the room.

Door was shot open by some weird creature and it sent lightning bolt flying towards him. Mui shifted sideways and bolt hit the wall instead of him. Then closed in towards the intruder and hit it's upper body while casting his signature jutsu.

"Fire Release: Heavenly Prison!"

Red marking appeared on the creature's body and it's chakra became restricted. When it seemed that the brief skirmish was over, however, dozen similar monsters appeared one after another outside of the laboratory, all charging towards him.

"Where did those thing cane from?" Mui frowned.

The beast he just subdued tried attacking him again, but it was clear that not only it lacked ability to cast any jutsu under the Heavenly Prison, but it's speed and strength had noticeable declined. However, no matter where he hit it, creature just wouldn't die. It just reconstructed itself again and again.

It wasn't until he managed to hit and break the mask that the creature fell apart and stopped moving.

Soon, other similar creatures were upon him, throwing wind bullets and fire attacks one after another, using compatibility between the chakra affinities to enhance the damage.

Mui steeped outside and blocked off the door to not let the intruders disturb the awakening process. He dodged and blocked most of the attacks, then appearing in front of closest spirit, he casted Celestial prison on it. This continued for a while, Mui avoiding jutsus thrown at him and swiftly immobilizing the masked creatures on after another.

However, there was a problem. The number of attacks didn't decrease at all. In fact, opposite started to occur. More and more of those creatures appeared in front of him.

While Mui was an experienced jonin, he possessed limited stamina and chakra. More the battle dragged out, worse his condition became. Burn marks appeared on his body, his breathing became heavy. And when the relentless attacks forced him to move away from the door, creatures managed to slip inside the laboratory.

"Moroi! Get rid of that thing, now!"

Mui continued to fight. He had already destroyes dozen of those beasts and immobilized thrice that amount yet there was no end to them. He couldn't understand how this many monsters managed to infiltrate Hozuki Castle. There weren't many who could instigate something like this.

Suddenly, the creatures fell back and stopped to fight. This puzzled Mui but then he sensed another presence approaching.

The creatures gave way and two person walked out from within. A woman and the men who slowly approached him.

"You can go ahead. Just leave Mui to me. I'll deal with him." Ruyzetsu said.

"Sure, that was our deal after all." Came voice from her side.

Kakuzu ignored Mui, who desperately tried to stop him from advancing but was thrown back with a kick and before he could manage to attack again, he was cut of by Ryuzetsu.

"You're not getting any further."

• • •

As Kakuzu stepped inside the laboratory, he noticed Sora, and the chakra that was extracted from him and transferred in inside a certain box.

He approached the boy and cut of the chakra connection. Sora was quiet, it seemed that he had lost his consciousness.

"You know that I noticed you, right?" He asked out loud.

"Hey…" Came an awkward voice from the corner.

A person who stood there had raised his hands and was bitterly smiling.

"…"

"I don't have any loyalty with that dude, you know. I just did what I could do to survive. There nothing I can do against you or dozens of those monsters outside. I give up." The man said.

"Just stay quiet and don't move. Understand?"

The man nodded in response and froze on the spot. Kakuzu tied man's limbs and turned back to the table in the middle of the room. He stood over Sora and raised his hand, on top of his heart.

Pseudo-Jinchuriki are rare. Extremely so. And only reason they don't immediately die from tailed beast's chakra is because of their special constitution. Meaning, you're exactly what I was looking for.

He pierced Sora's chest and cast the jutsu that soon drastically changed how the boy looked. After a while the process was complete and Kakuzu took out wind affinity mask that he placed it on the rising mass of the tentacle-like threads.

Next moment, a spirit that Kakuzu estimated to have around a rank B heart stood in front of him.

This made Kakuzu somewhat excited and interested. After all, this was first rank B heart that he had taken and he wanted to find out how much difference it could make.

A rank D wind spirit came out of his back and new one took its place as his vital heart. He cut complex connection with rank D one that only made with the vital hearts and replaced it with rank B spirit.

Suddenly, he felt intense surge of chakra that made his hearts beat intensely for a moment. After calming down, he took notice of changes that new heart caused:

His direct chakra reserves improved greatly to the point that it exceeded amount he had when he possessed five vital hearts in his chest.

Along with that, the density of his chakra had also increased. Meaning that potency of his attacks would increase. Finally, his chakra flow became more smooth, making it easier for Kakuzu to control it. If he made a comparison, at this moment, he by himself, would be at around level of Jiraya.

He then turned towards the guy sitting on the nearby chair.

"So, what am I going to do with you, now…" Kakuzu thought out loud. He remembered this character before him, and he had left some impression on him.

"Hey, there's no reason to kill me, man. I'll do anything. Just don't turn me into the same thing as you did with that boy." The man answered with a slightly horrified expression caused by what he had just seen.

"Hmm… I could use some capable subordinate. but I need some assurance that you won't betray me."

"I'm a man of the circumstances. I'm sure we can come up with something." The man said.

"Well, why not, let's give this a shot. This creature laying over there is a mindless puppet, having no will of their own. If you're lucky, you'll retain your sanity, and your appearance." Kakuzu calmly explained.

"I'm not sure I like sound of it. What are chances of my survival?" The man asked.

"It depends." Kakuzu answered as he approached the man. "If your will is strong enough, you'll survive."

Threads restricted the man and pierced his chest.

An D rank, huh. Not bad.

"I don't have much time. And you don't have choice either. Let's get over with this." He said as the threads encircled the heart and muffled screams of the man could be heard. "Hang in there. This is going to hurt a bit, after all."

• • •

Outside of the laboratory, number of the spirits could be seen encircling two figures. A man and women were fighting to erase their regrets and accomplish their desperate wishes.

The man wanted to summon a beast, and revive his long-dead son that he killed without knowing how much he would regret his actions.

The woman wanted to kill the man, and avenge his long-dead childhood friend, who had pointessly died because of clan's cruelty.

And the scales of the fight seemed to have fallen on the woman's side. Mui outclassed her in nearly everything. Be it a skill, strength or experience, he was far superior than her. However, as he was in unfavorable condition, he was greatly weakened.

It was made apparent how tired he became after fighting dozens of the monsters when he couldn't dodge her attack and fell to the ground. He was unable to stand up and as the girl approached him, he became sure of his demise and the failure. Deep sense of grief and regret made its way towards his expression and a tear fell from his eye.

"Please forgive me Muku, for being such a terrible father…" He whispered to himself as his greatest regret flashed through his mind.

Ryuzetsu's steps halted for a moment, but her determination couldn't be broken by such an useless words. Even if Mui regretted his actions, that would change nothing.

She grabbed the man by the collar and after lifting it up she slashed kunai towards his throat.

Blood splattered on the floor, but man didn't scream or try to cover the wound. All he did was mumble something that were impossible to make sense of.

As she stared at dying Mui with a complicated expression, spirit stepped forwards and grabbed Mui's torso.

"May I?" Asked the spirit.

"Yeah. It's over…" She said quietly.

• • •

"Are you alive over there?" Kakuzu asked, though he already knew that result was success.

A man was laying on the floor and breathing heavily, unable to regain his focus.

"Stand up. It's about time."

The man seem to have regained some clarity and rose up in sitting position.

"Ha… fuck, man… that was hell." The man said absentmindedly. "I can steel feel pain. What the hell did you do to me?"

At that moment loud crash resounded throughout the laboratory, followed by loud roar from the wall.

"You can check it out later. Get out of here first." Kakuzu said.

The man stood up with difficulty, seemingly having trouble with controlling his body. But he realized that something troublesome was going to happen, so he run towards the door and escaped to safety.

"Alright boss. Take cate"

With that, the man disappeared, and Kakuzu shifted his attention towards the box.

"I thought it would never open. But it seems that chakra was enough, after all."

Walls of the laboratory started shaking and soon small earthquake begun to engulf the castle.

"Now then, shall we see if this jutsu of mine works on you as well?"

Kakuzu stood before the shaking box that was causing all of the sommotion.

Satori was on the verge of the awakening.

{Chapter End}

I want to explain the ranks in case it's confusing.

The rank that Kakuzu assigns an individual is entirely his estimation and is based on the chakra volume and density that the individual possesses. Meaning that while higher rank means better potential, it doesn't necessarily mean that it determines who is stronger. Like how kid Naruto can have more chakra than Kakashi but can still be weaker than him.

Alright, that's the end of today's lesson. Also, feel free to share your thoughts about the story. I would greatly appreciate it.