Use activation tags "faceinsheath, oral, sheath play, sheath, fully sheathed, animal genitalia"

IMPORTANT! ALWAYS put "close-up, faceless character" either in the negatives (if you want both charater's faces to be visible) or in the positive (if you want just one character's face to be visible), if you don't use these tags there is a high chance that you will get weird, broken anatomy/amalgamations.

Also recommend putting "neck bulge" in the negatives because sometimes it pops up unprompted randomly.