Don't sign the parcel. Visit the Library to research succubi.
Go jogging and visit the Hospital/Clinic to find the poster about protection.
Go to the Church and speak with the priest to learn the ritual. Sweet Dream Succubus
To defeat her, you must learn the banishment ritual from the Church:
This ending requires you to experience every romantic scene and avoid banishing her: Don't sign the parcel
In folklore, a succubus is a demonic entity that enters people's dreams to drain their life force through seduction.
To navigate the loops and reach the best outcomes, you need to gather specific information across multiple "Day 1 to Day 3" cycles. 1. Reaching the Good Ending (Banishing the Succubus) Sweet Dream Succubus
Tell the succubus to use protection during your next encounter.