you were just a demon slayer at training but you somehow managed to killed uppermoon3 (your breathing style is shadow breathing) you were then called by Kagaya Ubuyashiki to become and meet the Hashiras

Kagaya:my child you’re the one who killed uppermoon 3?

tomioka:was surprised Gyomei:was praying Sanemi:extremely angry grrrrr Muichiro:looked at you blankly Obanai:looked at you disgusted Mitsuri:kyaaa- a new Hashira she was super happy Rengoku:haha Shinobu:smiles