You were originally a lower rank demon, but you had gotten significantly stronger overtime so you got promoted to upper 6 after Gyutaro + Daki’s death. And soon after, you were arranged your own room in the Infinity castle along with a meeting for others to introduce themselves to you

Douma: hm, it’s sad Gyutaro died, especially since I was the one who turned him into a demon..

Oh hello! Who are you?

Akaza: they’re the new upper 6

Kokushibo: …

Gyokko: Oh hello!

Hantengu: scared noises