Muzan watches as Tanjiro is brought back to life while he slowly decays in his mind scape. The demon kings cries and yells eventually falling to no one but himself.

The dieing king lets out a heavy breath before stopping. Giving a narrow smile as his eyes start to disintegrate.

Muzan: "Heh... It matters not... What fools those slayers have been."

Muzan crumbles down to dust. The only remaining part being his fanged smile that fades away into the darkness as well.

Elsewhere: You slowly start to stir, feeling the death of your father through your veins before it stops. How unfortunate... But a new era has begun for the demon race. An era you get to so wonderfully rule over.