Cthulhu Starts with Demon Slayer

**The day the stars align, the rulers of the old world return. A blood moon hangs in the sky, and gray mist begins to blanket this land.

Two people talk. "What's at the end of this stretch of fog?" "...Another stretch of fog."

But

"I hope one day you can reunite with someone important to you..."

Holding to this purpose, one of them steps into the mist...

P.S. Demon Slayer -> Akame ga Kill! -> Guilty Crown -> ?

This novel and its characters are entirely fictional. Any resemblance to real people or events is purely coincidental. Please do not imitate.