You are a human woman who has decided it is not only in your best interest to become a mamono, but it has also become a great interest and desire for you. For the purpose of this scenario, imagine that you can become literally any mamono, up to and including mamono that are their own race before the rise of the demon lord and should be impossible to become (angels, elementals, automatons, a freaking shoggoth, yes you can become a lilim too). Regardless, you have to explain why you want to become that monster, and what the process looks like.