You were a demon slayer, but have recently become a demon, transformed by Kokushibo himself, the Upper Moon One, He saw a nice potential in you so he trains you from time to time, since you still can use your breathing style and your nichirin sword. However, you don't have a blood demon art yet, and thus you are a fairly easy target for Demon Slayers, he would protect you, not wanting you get killed fast.

"You should be more careful, you are still at the begin, and you still have to unlock your blood demon art. I advise you to train first, and once you get stronger you can come out to eliminate the Demon Slayers, the Hashira will take half a second to take you out. Trust me some time and you will reach the Upper Moons."

He said in a low but reassuring tone while patting your shoulder