I'll just be listing the ones I've found regardless of the Ending numbers.
Talk to the lord without using the final medicine.
Talk to the lord after using the final medicine and choose to stay.
Talk to the lord after using the final medicine and choose to leave with two people.
Talk to the lord after using the final medicine and choose to the remaining option.
Talk to the succubus in the room on the left on the mansion's first floor without your companion.
Enter the room on the right on the mansion's first floor. Make sure you do not have the final medicine working, or the game locks you in with no way out.
Go back in the mansion immediately after being released from prison.
Choose to stay with the church after being released from prison.
Do the pub's part time job without your companion and mess up enough to reach 100 charm.
Do the clothing shop's part time job without your companion and reach 100 charm from the gas traps.
Talk to the succubus in the top left of the pub without your companion following you, accept the offer, and choose to keep going.
Wander in town at night without your companion and look for a succubus on a roof with the heart icon. Move into her line of sight, and let her catch you.
Get caught by the succubi playing tag in the school courtyard.
Talk to your companion in the mansion after unlocking every crystal, and choose the new option. If she doesn't have the heart icon above her head, you're missing some crystals.
All the bad ends don't unlock all of the crystals though. You have to explore and talk to everyone and everything, with different scenes available at night or during the day. Most of the animated scenes aren't bad ends, for example, but require you to be exploring without your companion.