Last time in was reborn in demon slayer as an Uchiha
he touched his neck and saw the blood before he got a bit enrage and then he remember that Yuichiro was flying toward him.
He got the time to move his head to the left as half of his neck got cut off by the boy, thankfully he started to regenerate it but he suddenly got his on the other half of his neck as Muichiro slashed it.
He used his hands to kept his head from falling as it was healing but Gyomei flail hit the head as Sanemi slashed both of his hands.
His head went flying as his body stood still with no head or brain to pilot it.
A new head started to form and Muichiro and Yuichiro were already rushing back at him.
Gyomei and Sanemi made sure that his hands stayed cut while the twins made sure that the head never fully regenrate before they cut it and this cycle continue for a full hour before Kokoshibu's body disintegrate into ashes and flew away.
Now we continue where we left off.
"Huh, do you honestly think you can beat me" Atoru said looking at the demon and from the look on Muzan's face he could roughly guess the answer.
He then notice something else, Muzan cell were moving in a weird way like he was going to...
As soon as the idea pop in Atoru mind, his left and right eye started spinning like crazy and the demon king suddenly felt like he had lost the ability to regenerate and to explode into a million pieces.
"You are cowards if I have ever seen one," Atoru said looking at the demon.
"You a fucking coward, you talk big and thought and say a lot of shit while acting high and mighty and now that it looks like you are about to lose, you are considering running away, you my dear sir are a fucking coward," Atoru said getting closer to the demon.
"It doesn't matter what kind of ass pull you pulled out your add next your are not getting out if here alive, I will kill you"Atoru said slowly getting closer to the demon with each word he spoke.
"Who are you to call me a coward when you are nothing without me"Muzan said looking at the teenager in front of him.
"Without me you wouldn't have any of your techniques, you wouldn't have any of your fancy ability," He said to the teenager that was starting to get very close to him.
"I beg to differ," Atoru said still walking toward the demon.
"If you kill me, all of your precious eye power will disappear and you will be nothing than just someone that is above average"Muzan said to the teenager and it was clear that he was getting scared.
"I'm sure that you love you power and would like them to stay and as long as I'm alive, they will stay with you"The demon king said again trying to persuade the kid that his power are someone still li led to him.
"If I'm being honest I frankly don't care, if they all vanish after I kill you, all I know however is that your blood has been passed down in my clan for generation and as such your hold on us grow weaker with each generation," Atoru said before he got into slashing distance.
The demon seeing that his lies will no longer decided in a last ditch effort to release all the power that he had in his body, he didn't care if the power surge killed him, he just wanted to kill that smug teenager.
A crack appeared on the floor as Muzan was already in front of Atoru who just proceeds to bitch slap him away sending the demon king flying far away.
As the demon land and try to regain himself the teenager was already behind him and before he could do anything, the fist of the teenager were already printed into his back which caused him to puke out some blood.
The demon king then notice a vein appear on Atoru's neck and a smile started to appear on his face, it seemed like the boy was about to reach his limits and all he had to do was to wait it out.
After that revelation, the demon king proceeded to fight from afar and to not get too close to the boy as he did not want to get too badly beaten up.
Time skip 30minutes
As the fought a small smile appeared on Atoru face as a bunch of variation of the rasengan and rasenshurican appear above him before he proceeded to condense all of them into one singular rasenshurican.
The power it radioated was massive as the rasenshurican seem to have it own gravity pull, and seem to be like a mini black hole because of how much it was sucking it.
"Thank you for being such a dumbass and falling for such an easy trick," Atoru said as he launched the attack and the speed that the attack reach him was just fast as he just saw the balk above his head before he suddenly felt his body getting destroyed to shred down to the atomical level.
'I still have one more sharingan'He thought before he notice that all of them were closed and that he had used all of them in his previous fight and before he could even reach, he had been completely destroy living nothing behind.
The technique still continue for a while after he was gone before it stopped.
Atoru sharing an seem to go back to normal as the 'veins' that muzan saw disappeared from his body and he looked brand new like he hadn't lose any energy at all.
He then looked at his hands that have been cut beyond belief because of long he been holding the attack and notice all the burns and cuts on his hands before he signed and said" I'm going to get a lesson about this"
Atoru vs Muzan (Obvious winner Atoru)
The infinity castle suddenly started shaking as it started to fall apart while I slowly drift in and out of consciencesss as I had used way too much chakra to kill him, a simple rasenshurican could of destroyed him but I just had to flex and use my strongest attack and now even though he is dead, my hands are numb and my fingers seem to not be moving and I feel like Kanae not going to like hearing about it.
A/N I'm be honest, The fight with Nakime would probably be the one that end last because as soon as she die the infinity castle would be gone as she was the one that made it with her blood demon art and so with No Nakime that mean no infinity castle.
I hear you questions like Muzan would of copied and to that I say, No for the obvious answer of he would of prioritize getting shit that make him stronger and stuff that he could use to kill Atoru for obvious reasons.
So I'm conclusion, Nakime die last as I don't want to create some forced drama where he has to protect people while fighting Muzan as I feel like I have already maxed my credit card on the amount of stuff that I can pull from my ass before someone call bullshit.