Big Mom looks at Y/n as she realises something.

Big Mom: You...have the form as Kaido don't you?

Y/n: Yep. I tend to not use this form because it makes me feel like I'm just like Kaido. But I have to use this form...

He readies his two swords

Y/n: To end this!!

Big Mom smiles

Big Mom: Come at me with all you have got!!

Y/n rushes at Big Mom as he uses his advanced conquerors haki coating as she tries to slice Big Mom but she blocks it with Napoleon. 

Big Mom: Take this!!

Big Mom uses her advanced conquerors haki as she slashes Y/n in the chest as he starts to bleed.

Y/n: Tch!! Take this!!

Y/n uses his sword as he swings them at Big Mom as they slash Big Mom in the chest as she coughs out blood and goes a back a bit.

Y/n: Lets take this a notch!!

Y/n and Big Mom go back and forth just slashing and attacking each other. Both of them are losing a lot of blood as they are just going blow for blow.

Big Mom: Ikoku!!

The shockwaves send Y/n as he crashes into a mountain. Y/n wriggles out of the dent he made as he comes right back

Y/n: Yaaaa!!

Y/n uses advanced conquerors haki coating as he continuously to just slash at Big Mom as she is bleeding as well.

All of the Big Mom pirates are just looking at this battle absolutely amazed

Oven: This is just a battle of who can last the longest...

Galette: This is the battle of the mons-

Smoothie: Breaking news guys!

Smoothie comes with her subordinates

Oven: What happened sister?

Smoothie: Katakuri has just lost...

Galette: Huh!? How!? To who!?

Smoothie: He just lost to Straw-hat Luffy

Y/n hears that as he smiles

Y/n: So Luffy-dono...you wanted to take out Katakuri-niisan while I was fighting Big Mom! Just stay safe...

Big Mom looks at Y/n as she smiles

Big Mom: Looks like you are getting stronger and you are even able to keep up with me unlike those other times!!

Big Mom prepares herself

Big Mom: This where you will perish Y/n!!

Big Mom grabs Prometheus

Big Mom: Stolen Feuer!!

The attack comes towards Y/n

Y/n: Blaze Two-Sword Style: Imperial Flaming Wings!!

The two fire dragons go towards the Fireball as the two attacks clash as an explosion goes up into the air.

Everyone is just shocked at the scale of the whole explosion. Big Mom looks towards Y/n and starts to laugh

Big Mom: Where is your kanabo Y/n? I thought you use to use those!

Y/n: I am not kaido so why would I even want to use them anymore.

Y/n blitzes Big Mom as he used his advanced Ryou as he slashes at Y/n.

Y/n: I am the reincarnation of Kozuki Oden. I will defeat you...then go after Kaido's head after this is all done!!

Big Mom laughs at Y/n's cockiness.

Big Mom: Lets see what happens.

Big Mom runs towards Y/n as she starts to combo Y/n with her advance conquerors haki coating as she continues to hit him as he loses consciousness for a bit

Y/n gains consciousness as he starts to combo Big Mom as it is now just a fist fight to see who will be the one who is the last standing.

Y/n uses his ryou as he pushes Big Mom back.

Y/n: My turn now!

Y/n grabs his two swords.

Y/n: Blaze Two Sword Style: Omori Kyruuden!!

The dragon hits Big Mom as its stays with her as she goes flying into a mountain as the whole mountain just breaks.

Y/n: I am not done yettt!!!

Y/n rushes towards Big Mom as he uses his advanced conquerors haki coating as he just starts to slash Big Mom.

Y/n: I came here...to win..so that's what..I WILL DOO!!

Y/n continues to slash and slash her as she continues to lose even more blood.

Big Mom: Take this!

Big Mom gets pissed off as she grabs Prometheus as she uses him as a glove as she just punches Y/n as Y/n goes flying while Big Mom has also gone flying also.

Y/n: Damn...

Y/n touches his head as he looks at his hand as he sees blood

Y/n: I feel a bit faint..

Y/n falls as he gets down on one knee..

He looks as he sees Big Mom is on her last stand as well as Y/n.

Y/n coughs out more blood as he smiles through the pain and takes out his swords and stands up. Big Mom looks at Y/n

Big Mom: I've won Y/n!! What are you going to do!?

Y/n: I refuse to believe that...

Y/n looks up at Big Mom

Y/n: I am putting all of my power...

Y/n's swords get coated by Advanced Ryou and advanced conquerors haki

Y/n: INTO ONE LAST MOVE!!

Y/n coughs out some more blood as he looks at Big Mom absolutely determined as he runs at Big Mom.

The flames on his back were half off and half on.

Big Mom: I wont let you win!! ZEUS!!

Zeus comes to Big Mom's side

Big Mom: INDRAAAA!!!

A bunch of lightning bolts just come towards Y/n as they all just start to rain down on him.

Y/n: I have to win this!! And make it through!! 

Y/n uses his observation haki as he starts to dodge the attacks that he can but some of them he just cannot dodge them as they just hit him.

Y/n: Am...I going to make it...? Or am I just going to die here....

Y/n is bleeding all over as he is trying to find the reason to why he should push through all of the pain.

Y/n remembers that he told the others that he would come back alive. And that he would come back victorious.

Y/n: PUSHHHH!!

Y/n jumps up into the air as he soars in the air towards Big Mom

Y/n: GRAHHHHHH!!! THIS IS......FOR MEE!!

He continues to soar through the air as the lightning bolts continue to him. The fire on his back burns a crimson red as he looks at Big Mom

Y/n: ITS OVER....BIG MOOOMM!!

Y/n readies his swords with all of his strength

Y/n: TWIN.....DEMONLY.....DEPARTURE!!

Y/n fires off two demon departures as they both hit Big Mom sending her absolutely flying as she goes tumbling through the terrain as she keeps on going and going until she just stops.

Y/n sees her on the floor as he just smiles

Y/n: YOOOOSHAAAA-

A sharp pain inflicts Y/n

Y/n: ARGHHHH!!

Y/n feels intense pain as he transforms back into his base form as he just slams right onto the ground.

Y/n: I used up...so much power...

Y/n closes his eyes as he opens his eyes to see that he is  in some sort of green pasture.

Y/n: W-where am I?

He was on the floor as someone was just stroking his head and humming.

Y/n: AH!! Who are you?

???: You don't know me? I must have been a terrible mother..

Y/n looks at the woman

Y/n: Mother...

He cries as he hugs her

Hisu: Calm down Honey...its okay

Y/n: Am I dead?

Hisu: No...you are only half dead.

Y/n looks at his mother with tears in his eyes

Y/n: I found out what happened to you...what happened with Kiyonako!! And I swear I will get revenge!! For you and Grandpa

Grandpa: Oh If it isn't little Y/n!

Y/n: Hello Grandpa!

Grandpa: My My you have grown!

Y/n looks at his hands as he is fading

Y/n: W-what is going on!?

Hisu: You are going back to the real world dear..but just remember..

She hugs Y/n

Hisu: I will always love you..

Y/n cries as his consciousness finds his way back to his body as he looks around.

Y/n: Yoshaaa!!!

-With Big Mom-

The Big Mom pirates run over to Y/n as they see she is just completely knocked out.

Oven: He did it didn't he....

Amande: He did...

-Back with Y/n-

Y/n is barely able to walk as he is just limping away

Y/n: Gotta get...back...to the...ship...

The Battle between Lunarian Y/n and Yonko Big Mom. It ends with the winner of the fight is....LUNARIAN Y/N!!!

Thanks for reading!! and I hope you enjoyed this fight!!