Fun fact, there is a real vore cafe in Japan that does exactly this for real people. It uses moving balloons/inflatables and warm slime to simulate the experience. It's reservation only and it accommodates any special requests customers might have, and it has a shower at the end of it.
You...
@Joey102 reread the previous chapter, in it the aide was shown to have captured? possessed? taken control? of Undine using those demon pinky fingers or whatever so that he could take control of the city's water supply. so defeating him released Undine