[X] You're a parasite riding in Jaune's hollowed-out body. Hijacking what was once second-nature to him. His Semblance is just another function, right? No different than his muscles or his lungs.
[x] Jaune's soul isn't technically gone, not completely. You have enough of it left to raid for memories. His Semblance is just part of that, right? Utilising it should be no different.
[X] Pyre burns things away to fuel itself. Tuned it, whether consciously or unconsciously, to lick at the fat until it bubbled and hissed and melted away so that his comfort-eating would leave no more shameful marks than it already had. Why should you be any different? You have countless meals stewing within you, countless fragments of story in the well. Burn those as fuel.
[X] You're a parasite riding in Jaune's hollowed-out body. Hijacking what was once second-nature to him. His Semblance is just another function, right? No different than his muscles or his lungs.