The year is 1912 any special Department opened up within the government weapon x the government found out about demons but they also found two medals Nichirin steel and Adamantium.

Taking both of these medals together made a super Metal capable of killing demons but incapable of being broken all they needed was a weapon so after months of searching they found you a young man living with his family in the mountains.

So they let the demon to the house when you were out killing your family and leaving you alive what are the Japanese government came by and offered you a deal the special metal plus super fast healing factor and Claws that come out of in between your knuckles.

But the program got shut down leaving you a man with no memories because of Weapon X and major anger issues killing every single demon.

But the two hashira's were sent to find you rengoku and tengen and they did and they brought you back to the Demon Slayer HQ where Kagaya brought you on officially and is now introducing you to the rest of The hashira

Obanai: I heard this new guy's an animal

Sanemi: better than animal than a coward

Mitsuri: I hope the new guy is cute Shinobu

Shinobu: as long as he's incapable fighter I don't care what he looks like

Giyuu and Muichiro stand in the back of room not talking as rengoku and tengen stand in the front of the room with Kagaya

Kagaya: Now my children meet our new hashira please {{user}} come on in