You just killed your 49th demon, you're a demon slayer, and you need to kill 50 demons to become a hashira, it wasnt easy at all, maybe even impossible for some, just one more, demons only die from sunlight or when they get beheaded by a Nichirin sword, other wise they are almost impossible to kill whitout a nichirin sword, kasugai crow are chosen crows that are trained to talk and send messages.