{DISCONTINUED} Here We Go (Again)

Before the defeat of Muzan, The Hashira, and some other demon slayers, managed to convince the remaining demons(most of the upper moons) to go against Muzan. With their help, Tanjiro was able to defeat Muzan, but at a tragic cost.

After the fight, Tanjiro disappears, and is never found. That was until a few days later, when demons started reappearing. Now, the Hashira, along with the surviving demons and slayers have to try and fix this before it becomes a problem.

or
Tanjiro becomes the new Demon King and starts bringing demons back into the world, and the hashiras and slayers and surviving demons have to try and sort it out.