The new demon king (Completed)

In this story, Tanjiro wasn't able to become a human after the fight against muzan and becomes the new king of demons. Now in the modern era, tanjiro is attempting to create a serum using his blood to make his demons walk under the sun. But he discovers the new hashiras of the now demon slayer are the same hashiras he met in the past.

And that is when he gets worried, because he remembers their strength. But using whats left of his humanity to create a drug that will weaken him so much giving the slayers a chance to kill him. But most of his humanity is now gone.

The now modern hashiras remember their past lives and nezuko, Zenitsu, and inoskue remember their past lives.