Y/n POV

It's been a two weeks since I turned into a demon and for the most part it's been quite peaceful, and even though I've lost the ability to walk in the sun, I'm fine with it, I've always been more of a night person. Right now I was with Mika or now she goes by Kokushiba in a tower hidden deep inside a forest, and I'm laying on her lap while she is making my hair in braids, we had just left with Lord Muzan and he told to eat humans to grow stronger and create blood demon arts.

Kokushiba : "So how many people have you eaten tonight?"

Y/n : "I don't know, fifty I guess..."

Kokushiba : "That's good, but we still need to eat more if we are to even develop out blood demon arts."

Y/n : "It's slow but effective, I can feel myself getting stronger, but we still haven't run into any demon slayers yet."

Kokushiba : "Don't worry, I've already killed a few and eaten some, they'll all die by the age of 25 due to the demon slayer mark."

Y/n : "That's good to know. My mark always caused me pain."

Kokushiba : "Y/n, I think your mark makes you look cute~"

I then blushed a deep red.

Y/n : "Koka, I told you not to tease me."

Kokushiba : "Not gonna happen~"

I then covered my face while Kokushiba laughed at my reaction. 

Kokushiba : "So what are you thinking of creating for your blood demon art?"

Y/n : "I'm thinking of creating two blood demon arts."

Kokushiba : "Really and what are they?"

Y/n : "Well for one of my blood demon arts, I thinking of having the ability to create black fire that burns people over time and for my other blood demon art, I'll have the ability to create a black mist that would create illusions so that my enemies will have intense hallucinations and won't be able to tell what's real of not."

Kokushiba : "Now those are actually very deadly abilities."

Y/n : "If were gonna be upper demon moons, we might as well have abilities worthy of a upper moon demon."

Kokushiba : "I suppose your right."

She then stops braiding my and gets up. I get up as well, and we head out into the night to continue eating people to get stronger.

Time-Skips 70 Years

It has been 60 years since me and Kokushiba became demons and I have to sat its been pretty good, Muzan has made me Upper Moon Zero and has made Kokushiba Upper Moon One. We look pretty much the same except she has six eyes and i have four eyes two new eyes under my original ones. I also have a sword made of my flesh sword that I carry on my back. It was the middle of the night while we were walking back to our home after a night of devouring humans.

Y/n : "I wonder what Master Muzan is doing?"

Kokushiba : "I have now idea."

I smile at her, but then I heard something from up ahead and what I saw shocked me to the core.

It was Yoriichi... alive. Me and Kokushiba were stunned and shocked at the sight before us.

Kokushiba : "That's impossible! You should have died ages ago. The mark should have killed you!"

Y/n : "The other hasira died, why didn't you."

Yoriichi : "Sister, Y/n, why did you two have to become demons."

He then started to cry, me and Kokushiba were stunned to see him cry. In the time I've known him, I have never seen Yoriichi show any emotion. Yoriichi then reached for his sword, and charged at the two of us he went to strike Kokushiba, but I blocked him with my sword, he then went behind us and got ready to strike again, but he didn't get the chance because I cut him in half. But me and Kokushiba saw something that surprised she saw the flute she gave her brother when they were kids, and I saw the bracelet I gave him when we first became slayers. Even when we became demon he held us in high regard. It brought tear to me and Kokushiba's eye's. She took the flute and I took the bracelet, and we left.

to be continued...