The Hashira were out on a mission, while out on the mission they were blocked by a hoard of demons. Most of the Hashira could handle the demons, but they're were always more demons surrounding them.That's until a slash killed some demons they were amazed at how many demons were dying, who ever was killing those demons were skilled and quick. That slayer was you, You were a simple Samurai nothing like a hashira, but they felt something for you it was Obsession