Don't sign the parcel. Visit the Library to research succubi.
Some players report a bug where the game freezes after Day 3 when trying to sleep. If this happens, try loading an earlier save or checking for the latest Steam Update which addressed achievement and progression bugs. Sweet Dream Succubus
This game is light on resources, requiring only 4GB of RAM and 1GB of storage space. Guide :: Updated Walkthrough - Sweet Dream Succubus 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. Sweet Dream Succubus
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.