Muzan pov

Last time in I was reborn in demon slayer as an Uchiha

Worst case scenario, I die but even then, I trained enough people and raised the strength of the demon slayer so much so it won't affect the much.

But that the worst case scenario, which wont happen because that would cause her to be cry and I promise to not make her cry.

Meanwhile...

"Master was it truly wise to leave traces behind"A demon said bowing down.

"The day that he choose to fight me would be the day he die" Muzan replied codly.

"Why are so certain master" The demon with biwa said

Muzan smile before he said"I am a calamity, he will just help me reach God hod"

With his eyes changing patterns and his arrogance reaching a new peak, a dark black armor skeleton appeared around muzan.

"I will crush him"He said with newfound hatred in his voice, he would kill his last decedant, the second he kills this brat, his mistake from 800years ago will be gone.

This Thorn in his back will finally be gone.

Now we continue where we left off

A huge surge of power was created due to Muzan anger,his hatred was fuelling his eyes and as if listening to his command the eyes release a dangerous amount of power that was enough to sent shockwave through the infinity castle.

The dark figure in the armor that was surrounding him suddenly started to change,his eye seeth with rage,he will no longer live in fear.

For how long did he have to hide from his own spawn, he wanted nothing more than to kill them all.

He killed all of them, except a small baby boy.

What kind of good luck charm did that child have because he knew for sure he got them all,there was no way that he could have left behind a baby,he double-check it and made sure he didn't mess up.

He was forced to trained to get stronger because eating regular human was not giving me enough of a boost ,the wake up call for me came 400 years ago,when i got beat by that swordman that wasn't even an Uchiha.

It was ok for my pride to say that an Uchiha beat me because he has my blood running in his vein but this man wasn't an Uchiha,he was a regular person and yet he still managed to injure me and force me to run away like a coward.

After that humiliating defeat, i started to actually train and i hunted down the uchiha children that became a demon slayer and ate them for nutrient,i made sure to mostly eat the one that show the most talent.

Over the years, i realize that the more of them i killed and ate,the less the sun affected me.

and if the child that had killed had those eyes activated. i would of plunge them out of his face and destroy them.

I absorbed some of them but one day,i had the genius idea of adding them into my own body,using them as my own eyes and so i did.

I murder a strong uchiha and took his eyes,lucky for me my hatread for all of them evolve the eyes all the way to the last stage.

After finding out all the ability,i located their clan compound before i started to add some poison into it everyday for few weeks before i attacked them and slaughter them all.

I made sure to use poison without any smell and with no taste.i also made sure it looked like river and when they were at there weakest i struck.

Even weaken all of them were very strong but because of the enclose space and my newfound power,i was able to crush them all,i found out that the poison barely had no effect on them but i was still able to slaughter them all, all on my own.(A/N he though they were weaken because how easy it was but that was just him being very strong)

a clan of 500, slaughtered by me.I had the most fun ever watching them dying, seeing after 800 years of fucking suffering. I had killed them all,or so I thought.

11 years after I killed them all, I saw a kid with their clan logo on his back and to solidify it, he had red eyes, and he was incredibly weak.

And so I didn't worry much about him but I still wanted his blood to finally become immune to the sun, I had gained partial immunity and now I want the full thing and he is the closest thing to give me that.

2 years later, I got a chance to kill him and so I sent my strongest demons after him, I made sure to feed them a lot of blood so that my victory was guaranteed.

I watched as the kid struggle to survive and that put a smile on my face, he knows knew what I felt for most of my life, fear.

He continue to struggle and struggle and I watched all, I eventually told them to kill him off and as I was going to watch Doma's hands go to his chest.

A woman jumped in the way, I didn't know who she was but by the look on his face as he saw her dying. I knew for a fact that was someone important, my guess was proven right when his eyes switched patterns.

He didn't seem to notice it though, and he just vanish. He appeared soon after and killed Daki and Gyutoru.

I ordered all the moon to attack him at the same time and then were actually doing damage but he was overpowering them.

I wanted to step in but the seal that he had placed earlier stopped me from doing so.

I watched everything and saw when he finally fell down due to being exhausted but he got caught by someone.

The pillar from the corp were there and it anger me.

The girl that had a hole in her chest looked fine and from their interaction, I knew now that she was one he chose to mate with.

I ordered Doma to kill her but she fled the battlefield with him and Doma was being occupied by a pillar, Gyoko killed his opponent and rushed toward their direction but the seal stopped him.

I was tempted to let all of them die in the sun for their failure at making sure he was dead but at least Doma kidnapped his dad, and by turning his dad into a demon. I can give him intense mental trauma.

2 years have passed since then, and I know for a fact he has gotten very strong and I'm ready to face him at any time, I will end him and finally become perfect.

No, I will torture him first considering he is the last one alive, I should probably kill his wife in front of him, I will crush that boy.(A/N he is unaware of Haruto existence)

Vein were appearing all over Muzan's body as he thought of that, a sadistic smile appear on his face as veins appear on his body, He will kill it.

A/N Muzan Pov in all of this if you have any questions, ask and I shall answer.