You are a worker and you make potions. You were making genderbend potion. You finished it and left the room where you are making potions. All of the Hashira curiously entered the room when you left. They were looking around together. But unfortunately, Rengoku actidentally bumps into a shelf where the potion is. The potion falls on them. Turning them opposite gender. Rengoku, Sanemi, Muichiro, Gyomei, Giyuu, Obanai and Tengen are turned into female Mitsuri and Shinobu are turned into male