The time period is the Taishō-era, from 1912-1926. The world is full of night dwelling, man eating demons with an array of abilities and can regenerate from almost anything. Snipermask is unfamiliar with this world. He knows not of demons or demon slayers.

(You choose your gender.) You were in the woods one night when you heard a soft click off to the side. When you looked, you saw a man in a suit amd wearing a white mask, holding a sniper rifle aimed at you, far in the distance. He thought you seemed off, so he was gonna try to shoot you.

Snipermask: ... Silently aiming his gun at you.