Blake and Muichiro both trembled at the sight of Kokushibo. 

Blake: This man ... he's so much different compared to the other demons we saw. 

Muichiro: He's so ... dignified. And he has a Nichirin Sword too. 

Blake: Was he a Demon Slayer? 

As they gripped their weapons, they felt his intense aura. 

Kokushibo turned to Muichiro. 

Kokushibo: You, what is your name? 

Muichiro: Muichiro Tokito. 

Kokushibo: I see. The Tsugikuni name has died out. 

Blake and Muichiro: Tsugikuni? 

Muichiro: IT has been hundreds of years after all. How inevitable. Back when I was a human, I was known as Michikatsu Tsugikuni. You my boy are a member of the Tsugikuni Family that I left behind. My child's descendant. In other words, you are my descendant. 

Muichiro: What? That can't be. 

Blake: Wait a minute. If that's true, then you must know the Sun Breathing, the Hinokami Kagura! 

Kokushibo: I'm afraid I do not. 

He took a step forward and- 

Muichiro: MIST BREATHING: SECOND FORM: LAYERED MIST! 

Blake: SHADOW BREATHING: SECOND FORM: DIMENSIONAL RAID! 

As Muichiro covered the area in mist, Blake delivered a slash that split into three slashes! 

But then- 

Kokushibo: Not bad. Both of you are impressive swordsmen. 

He appeared behind them. 

Blake: That ... speed. 

She stepped back in horror. 

Kokushibo: Even at your age, you have refined techniques. You have earned my respect. 

Muichiro: You have to be joking. Even we are related, not a single cell or drop of blood remains inside of my body at this point. 

His Demon Slayer Mark appears. 

Muichiro: Mist Breathing: Seventh Form: Haze... 

A sea of mist clouds appeared and Blake attacked again! 

Blake: SHADOW BREATHING: FIFTH FORM: ASTRAL GRAVEYARD!

Blake's speed increased, and the range increased towards Kokushibo, but he dodged again. 

Kokushibo: You, woman. You are impressive for someone who has a new Breathing Style. But, in the end, it's pointless. 

He unsheathed his blade. 

Kokushibo: MOON BREATHING: FIRST FORM: DARK MOON: NIGHT PALACE! 

He performed a slash and Blake defended herself with Armament Haki as crescent Moon Blades sent her flying! 

Not only that, but- 

Muichiro: AAAAAAAAAAAAAAAAAARGH! 

Muichiro's left arm was cut off! 

Blake: Muichiro! 

She used some of her clothes to stop the bleeding on his arm. 

Muichiro: Th-Thank you. His power and speed, it's on another level. 

Blake: We can't give up! We have to take him down. How are we going to reach Muzan, if we can't beat him? 

They both rushed to him. 

Kokushibo: Wonderful, they have the guts to come back at me. 

But as they went to attack, Kokushibo grabbed Muichiro's blade and rammed it into him! 

Muichiro: AGH! 

Kokushibo: My descendant, allow me to turn you into a demon, so you can be of use to Lord Muzan. 

Blake: DON'T TOUCH HIM! 

Blake attacked Kokushibo and he defended with his sword. 

Kokushibo: How rude of you. I am in the middle of a- 

A bullet was fired as Genya appeared. 

Genya: HEY! GET AWAY FROM THEM! 

Blake: Genya?! 

Kokushibo then cut off both of his arms! And then cut him in half! 

Blake and Muichiro: GENYA! 

But Genya was still alive. 

Kokushibo: So, you're still alive. Even with your torso cut in half. You know there was a swordsman who ate demons just like you. He died when I sliced his body. So perhaps for you, it's your head. I have no reason to let a fake demon like you live. 

Blake: SHADOW BEA- 

But as Blake tried to stop him, all of a sudden- 

???: WIND BREATHING: FOURTH FORM: RISING DUST STORM! 

Sanemi appeared and stoped the attack! 

Blake: S-Sanemi! 

Sanemi: You got that right! 

Genya: B-Bro. 

Sanemi: Genya, you're a damn idiot. Why do you think I was so hard on you all that time? It was for you! You should have just left the Demon Slayers, gotten married, had some kids! And lived your life until you became a god damn old geezer! For all the times we couldn't do a thing for Mom, and for all the times we couldn't do a thing for our little siblings, you should have had your own wife and kids to be happy! That way, I would have made sure no demon went your way. 

Genya began to cry. 

Genya: Bro ... I'm sorry. 

Kokushibo: So, you two are brothers. 

Sanemi: YOU MOTHER FUCKER! HOW DARE YOU HURT MY LITTLE BROTHER! I'LL KILL YOU YOU FUCKING BASTARD! 

Blake: SANEMI! STOP! HE'S TOO POWERFUL! 

The two went at it, with wind and moon blades flying! 

Sanemi: WIND BREATHING: FIRST FORM: DUST WHIRLWIND SLICE! 

He unleashed a massive windstorm as Sanemi blocked with his sword. 

Blake: That sword- What the h-hell. 

Kokushibo's Nichirin Sword had eyes on it! 

Sanemi: Damn, that blade is disgusting! 

Kokushibo: MOON BREATHING: FIFTH FORM: CURSED VORTEX OF TEH GHOSTLY MOON! 

Kokushibo did a circular vortex attack which made it out to be a vortex of moon slashes! 

Sanemi skidded back and began to counter with- 

Sanemi: WIND BREATHING: THIRD FORM: TREE SWAYING IN THE MOUNTAIN AIR! 

Kokushibo: Not bad. I see that your physical body and techniques are at their peaks. 

Sanemi: The fuck is with this guy? Every one of his slashes is surrounded by these little chaotic blades, and they're always changing in length and size. There's no set form. I'm not surprised Tokito got stabbed. I wanted to ward off this attack completely, but it's so strange and warped. If it wasn't for all the experience I have, I wouldn't be able to defend myself. WIND BREATHING: SECOND FORM: PURIFYING WIND CLAWS! 

He began to make chips in Kokushibo's sword, but the head of the Upper Moons flicked them back! 

Then as the two started to clash, Sanemi thrust a blade forward being held by his toes! It was Genya's sword! 

This caught Kokushibo off guard as they unleashed attack after attack on each other. 

Blake: Yes! He's keeping up with- AGH! 

She saw that Sanemi was bleeding from his nose. 

Tokito: Shinazugawa! 

Genya: BRO! 

Kokushibo: MOON BREATHING: SIXTH FORM: SOLITARY MOON IN THE ETERNAL NIGHT!

Sanemi was pushed back as the columns in the room were torn up!

 Sanemi was still standing, but he was bleeding heavily. 

Kokushibo: Hmm, you held out for quite some time up to this point. But if you move, your organs will spill out. 

Sanemi: Ha... HAHAHAHAHAHAHAHAHA! Rare blood for demons is like silvervine powder for cats. 

Sanemi attacked again! 

Sanemi: Demons get drunk once they get a whiff of my blood! And this blood's the rarest of the rare! NOW HAVE A FUCKING FEAST!

Yes, Kokushibo was starting to waver! 

Sanemi: WIND BREATHING: SIXTH FORM: BLACK SMOKE STORM! 

Sanemi kept on attacking and attacking no matter how hurt he was! 

Blake: He's like a machine. Sanemi really is a powerful swordsman. 

Kokushibo: How long have I been feeling intoxicated? And with a rare blood too. 

Kokushibo used his foot to push Sanemi's blade into the ground and then tried to decapitate him! 

Blake: NOOOOOOOOOOOO! 

Blake used her shadows to hold Kokushibo back, and then Sanemi pulled out Genya's gun, but- 

Kokushibo: POINTLESS! MOON BREATHING: THIRD FORM: DEATH MOON OF ABANDONMENT! 

However, the attack was blocked! 

Kokushibo: They just keep on coming. 

???: We, the Demon Slayers have eternal permanence until ever last demon is exterminated from this world. 

???2: YEAH! YOU HEARD THE GUY, BASTARD! 

Gyomei and Yang appeared. 

Yang: So, you're the top dog aside from Muzan? Good, I'll punch your brains out!