That sound the MC hears at the end is the Princesses vagina becoming flooded as an ocean and her doing/practicing kegels lol.

Yo.... I believe double cultivation does not look like this. From my understanding, it has to do with intercourse since it's the exchange of yin and yang energy and the dantian is located in the lower abdomen, so you can see...

Oh I know, that's why I said what I said because they're about to get it on off scene ahaha.