In Hex, you will play as a succubus possessing the former body of a mage named Meila.
Meila's spirit still clings to the body as well, and can't wander far, so whether she likes it or not, she'll be serving as a constant companion, even in the most intimate scenarios.
One of the game's core features (read: kinks) is Meila's constant presence. Her reaction to the protagonist's "activities" will slowly change over time, and her appearance in CGs will reflect her level of "corruption" (I don't like this word and it won't be in the game itself, but that's what other game's call it).
Please note that this artwork is incomplete, and the game is still early in development and things may change at any time.