After five days, some intense training with zero, rias and kuisha are quite tired and lying on the soft grass with zero in the middle of them and using his hand as a pillow.
Seeing the peaceful sleeping face of rias and kuisha and how they grab his shirt like their life is depending upon it, he can only smile worryingly.
He started to train them in basic physical exercise, because of there high bloodline they have much more demonic power than anyone as the same age and because of the low physical constitution, they are not able to use that power. Like when zero meet kuisha first time even though she has demonic power but her mind make her think that she exhausted her demonic power so that she can't forcefully withdraw more demonic power hiding depth in her body. If she really uses more of her power the consequence will be severed, even in worst case she can die by self-exploding.
That's why he started to train their body so they can use their full power and after their physical training end he then started to teach them controlling their demonic power so they can more efficiently use their demonic power. Even though kuisha's parents and her previous master teach her demonic magic and stuff but they don't teach her deeply about demonic power control and that's why her control over her spell is very low and consume more demonic power.
After he started to train them kuisha's parents dismiss her teacher so she came to their house daily with teleport circle and train with him.
After their training, like always using his hands they are sleeping soundly not caring for the world, It's like a routine for them.
While zero dazedly staring at the sky suddenly in his mind he can hear a report from one of his clone. Hearing the report something in his eye flash and zero slowly pulling-out his hand under rias and kuisha's head and bring them to their room and place them above the bade and cover them with a blanket so they can stay warm. Feeling like something is missing a frown appear on rias and kuisha's face and they reach their hand to search for something or someone and unable to find it they hug each other with a frown on their face. Seeing the loli hugging each other zero's dog blood staired up and almost has a nosebleed, but understanding that they are only seeking his residual warmth from each other he somewhat calm down.
"Are you sure that two young Nekomata child is transported to a branch family of the house of Naberius?" Zero asked whit a serious tone cause this news is related to kuroka and koneko.
"Yes, boss I personally investigate and confirm there are 90% possibilities that they are the one whom you are searching for." said the clone with a formal tone.
Hearing this zero search the clone memory and see exactly where the nekomata's are. Even though if he wants he can create a clone with whom his all six sense is connected and it will be like a second him but for some simple work like search party and exploration he really don't want to use it.
After locating the place where kuroka and koneko might be he hurriedly teleports near the place and thinking that if they are not kuroka and koneko he will save them secretly and if they are kuroka and koneko than he will do as his mood pleased.
After teleporting he found himself in a dark room, this room smell like shit and with it the smell of blood and chemical is on the air. It's a smell that is very familiar to him it brings back the memory he wants to forget but he knows that he is never able to forget because in this memory "She' also their. Remembering the past event and the familiar smell a cruel and dark smile appear on his face and killing intent surround him.
Founding him in dark he can use devil eye so to see in the dark but in True Sharingan eye it is nothing to compare of.
When he activated his True Sharingan eye, his iris turn a golden colour and five wheels like pattern appear which are composed of three blue tomoe, fifteen tomoe totally. Intense killing intent flashes through in his eye for a brief moment and gone away only to replace a pure cold look.
When he checks his surrounding with his cold eyes, he can see severely wounded bodies of human, best and non-human like devil, yokai..etc are lying in on the experimental table or in the test tube. Most of them have died and the look until their death is like they saw what is true disappear is.
Seeing deform bodies and the look on their eyes zero can understand how much pain they might have suffered until death.
He silently crosses the room and every stape he takes the killing intent surrounding him become more compressed and look like it will take a shape at any moment.
Until he reaches near the door he saw a little yokai girl of about fourteen to fifteen years old with black hair and two black cat-like ears on her head having a hard time breathing open her eyes sensing his presence.
Her body is not that much wounded but with his Sharingan eye he can see her internal organs are severely damaged and look they are rejecting her body like a foreign substance. And after molecular level observation, he can understand that they really are foreign substance and not her own internal organ. Even if he wants to save her with this foreign internal organ which is rejecting any cooperation it's only about time that she will die a painful death.
Seeing her open her eyes he approaches her and smile gently and slowly patting her hair asked: "It's very painful isn't it?"
Even though it's the first time she meets him and with the experiment going on and the pain that it brought somewhat makes her insane but for some reason, his patting brings her back from the insanity. she can feel that the time she can be sane is very small so she decides to answer his question "hum....it's v..e..ry pa..inf..ul" when she opened her mouth the pain makes her face disordered and she bearly able to say it.
Hearing her zero asked in the same gentle voice "Do you want me to stop your pain entirely?"
Understanding his words meaning she feel happy for some reason. It's her woman institute told her that dying in his hand and remember by him is her honour so she said "ple..ase"
"do you have any last wish then?" Zero asked her.
"ca..n yo..u ki..ll th..at mo.ns..te..r?" she said while slowly light of her eyes is fade away.
Zero gently close her eyes with his hand and whisper "Even you don't tell me I will show that bastard what true disappear means!!"
After exit the room, and approach the room where he senses the strongest demonic power presence in this underground experiment lab.
When he is near the room he can hear a rough voice of a little girl " Please spare my little sister. you can do anything with me!! please let my little sister go!!" with her voice, he can also hear the crying voice of a different little girl.
"Well if you cooperate with the experiment then I can release your little sister!!" he can hear the sinister voice of a man and determined the target to capture. Zero can understand the self-centre, arrogance and sinisterness mixed in his voice and he doesn't have any intention to hold his promise to the little girl.