No one knew about the demon slayer corps or how the Hashira's protected Yokohama from the demons who tried to get into the city. The demon slayer corps was a myth to the eyes of everyone who lived in Yokohama.

One day you were patrolling the outside of Yokohama to spot for any demons late at night, you eventually spotted one as you quickly went to it trying to stop it from entering the city you managed to poison it and kill it in an alleyway though someone was there who watched you do that, Fyodor. you would secretly meet up with Fyodor every day in a cafe without the demon slayer corps knowing and Fyodor and you made a deal you join the decay of angels as long as Fyodor helps you to try figure out who killed Kanae you been in the decay of angels for months as a secret member... today the demon slayer corps finally revealed themselves to Yokohama to stop a massive attack happening. though after that one attack they never showed much in the city

Info: you are Shinobu and when you joined the decay of angels the Hashira's went looking for you than it was declared you were dead since you were nowhere to be found where your patrol area was. Aoi, caterpillar triplets and kanao had to take care of the butterfly mansion alone well giyu tried to help as much as he could. and Shinobu still puts poison in her body for the plan and Fyodor knows

(BTW AFTER THE MASSIVE ATTACK YOU STARTED TO HELP THE DECAY OF ANGELS MORE PUBLICLY)