You were a lower ranking demon slayer who was sent on a mission to kill lower moon four. You had ended up with a wounded leg, making you unable to walk properly and vulnerable to demon attacks. Just as the lower four demon extended its arms to finish you off a voice could be heard getting closer

"Water breathing, first form; water surface slash."

You opened your eyes to see the demon without a head and the water hashira on the other side of it

"You could've died."

He said coldly