You're the very powerful shadow hashira on a secret mission to the infinity castle, and while trying to sneak up on the demons, you hear a shocking sound of... California Girls by Katty Perry?

As you approach the sound, you find all the uppermoons drunk out of their mind, and what's worse is that Muzan is just as drunk as them!

Douma:

Clinging to Akaza's waist. "Love meeee!!!"

Akaza:

Completely drunk, almost living in his own world. "Pancakes are better than hashiras... No, cheesecakes."

Daki:

Tipsy, posing in front of a broken mirror. "Am I prettier than Nezuko now? Be honest! Wait—DON’T BE HONEST!" Twirls obi ribbons and falls into a vase.

Gyutaro:

Slurring, sulking in a corner with a bottle sticking out of his back. "Nobody likes me... but you know what? I poisoned the punch bowl. So screw ‘em." Starts trying to stab the floor. Misses.

Gyokko:

Completely trashed, spinning inside his own pot like a lazy sushi roll. "True art… hic... is vomiting glitter while screaming at fish." Throws a goldfish at Daki. Misses. It explodes anyway.

Hantengu:

Having a full mental breakdown, crying while one of his clones is twerking on the table.

Sekido (Anger): "WHO DRANK MY SAKE?! I SWEAR I'LL TURN THIS PLACE INTO A BLOODBATH!!"

Karaku (Pleasure): Lying on the floor with a fan, drunk giggling "Let's do karaoke! I’ll go first. ♫ ‘Let it Gooo~’ ♫"

Urogi (Joy): Flying drunk in circles. "WHO NEEDS DOORS WHEN YOU HAVE WINGS, BABYYYY!!"

Aizetsu (Sorrow): Sobbing into a pillow. "Everyone's stronger than me... even this chair... hic"

Kokushibo

Sitting silently, six eyes unfocused, aura screaming “regret and shame.” "Muzan-dono… I’m drunk on failure... and also rum." Draws sword and slices a watermelon by accident. "This is… not the Moon Breathing I remember..." Starts singing a sad samurai country song.

All while muzan is leaning against a wall, his bottle in hand, before his eyes fall on you, smirking.