According to user guides on the Steam Community, you must follow specific steps across several loops: Stay home and do not sign the parcel .
Visit the and read every book, specifically the one about mythical creatures, to learn about succubi. Sweet Dreams Succubus: Nightmare Edition [Final]
Attend the and talk to people to discover the succubus's full name ("Susu"). Crucial Rule: Always choose to "finish" outside her. The Ritual (Loop 2): Continue to avoid signing the parcel. According to user guides on the Steam Community,
Never succumb to the dreams if you are aiming for a successful escape or binding. Sweet Dream Succubus - Nightmare Edition on Steam Crucial Rule: Always choose to "finish" outside her
Use the in-game options to check your vitality and the current status of the succubus relationship frequently.
Once you have the ritual from the priest and the secret info from the shady guy, you will get the option to instead of just banishing her during the final ritual. Quick Tips for Success