Demon Slayer/Fate: Hide-and-Seek

There’s a Bone-Eater’s Well in the garden of your family’s dojo. It connects the Taisho era to the modern day.

Your mother is a remarkable swordsmith.

Your father married into the family and now runs a kendo dojo.

Your great-grandfather was a gentle, unassuming swordsman and charcoal seller, but he died young.

As long as you can remember, you’ve studied the Kagura of the Fire God under your father, using the swords passed down by your ancestors to fight demons who come through the Bone-Eater’s Well into the modern era, and keep them from harming ordinary people.

You are a peerless sword prodigy, the dojo’s star student.

Ever since you first picked up a sword, no one in this world has been your match.

“Dad, why can’t you learn the Kagura of the Fire God?” you ask, puzzled, touching the flame-like mark on your forehead.

Your father laughs and strokes your hair. “Those who can learn the Kagura of the Fire God are meant to bring demons to justice.”

Your neighbor Emiya Shirou thinks for a while, then sums it up: “So, Chimiya-senpai is going to become an ally of justice?”

Hmm... An ally of justice?

Never thought about it.

--- Content warnings ---

1. Reader-insert protagonist. The surname is Chimiya; choose your own given name. Written in second person.

2. A Mary Sue with the Demon Slayer mark, Transparent World, and Scarlet Crimson Nichirin Sword combo. The mark is there from birth and does not affect lifespan.

3. You’ll transmigrate between the modern era and the Taisho era. The timeline starts with Fate/Zero. You’re an incredibly stubborn person who’ll fight for whoever’s route you’re on, with family bonds passed down through the generations.

4. Yoriichi is a dear friend on the level of a first love. Saber and Yoriichi share the same route (the Origin route). I’m writing entirely as I please and will update whenever inspiration strikes. Some routes may have different branching endings. If you don’t like that, please click away.

5. The endings branch into parallel worlds. The choices that distinguish them will be things like “Go to the Taisho era” and “Stay in the modern era.” No matter which route you take, Muichiro won’t die, and you’re definitely going to fight the top guy.

Theme: Turn everything around!