Turning to the past [Demon slayer Various X Female reader]

Getting reincarnated into demon slayer wasn't something you expected.
For the first 3 years you didn't even know you were in demon slayer. All you knew is you died and then woken up as a baby.
Then when you were 3, you met tanjiro.
Right then, you knew everything would change.
Completely, so in that moment you vowed to change what was written in the mangas.
You vowed to fix all the deaths and pain.
But would you?
Or would you make everything crumble and result in the death of millions.
You might have be in the past, but you are about to change the future