If I recall in the manga people turned into things after trying each other's cooking or something?
Near the end of the manga the female antagonist turned into air and tried to suffocate the protagonist, but stopped for some reason. Her henchmen used her to inflate a blow-up doll (it had clothes on so worksafe) to give her a sorta physical form.
However at the very end of the manga she was just left in the middle of a forest stuck inside the blow-up doll.

Pic only semi-related as it reminded me of it.