i believe it's exclusive to Demon King who can start it the same way anybody starts the 69 (you lie supine, she goes Plopping Down, you endure)
Viewing post in How to get into the autofellatio stance?
ouroboros? I don't know which scene is that
I unlocked almost everything, just these scenes are still a pain for me to unlock and nobody answers me when I ask for help, if you guys know anything please let me know
https://itch.io/t/2126603/help-missing-gallery-scenes#post-5918363