Syd, Kal, Azul, Zaine, Koga, your landlady and everyone at the Vore Center (maybe some I'm missing) all have at least one scene where they can eat you and you get let out later. All of those do however have a risk of getting you digested though (or unbirthed by Seras in Azul's case), depending on your choices, so there is no completely safe vore scene.