So I decided to dig into the game to uncover the secret ending and here’s what I discovered (I won’t spill the beans completely until 2 weeks):
1) Lily is last, and you must have a Jar on hand
2) You must fail a certain way to continue with one other requirement
3) Certain actions related to the end goal raises suspicion of everyone in the room, fewer raise fear as well
4) Some events raise either suspicion, fear or both globally
Edit: Been longer than 2 weeks but here it is: To get the true ending, you must get the suspicion fail route for Lily with only a single person in the Temple.
If done correctly, instead of receiving a game over for Lily leaving, you’ll instead be able to visit Lily in her room (from the first night) and chat with her. If given the choice during this conversation, admit the truth to her and she will render you aid. She does this by globally reducing suspicion of everyone.
Once you done this, queue up everyone but Lily and 1 other person for the temple, preferably all at once. If done correctly, there should be 2 people remaining on the 5th day: Lily and someone to give a jar to.
To quickly trigger Lily suspicion, perform actions in Lily’s presence that don’t cause her to go to the temple. An example is picking up the item in the Piano room.
If all done correctly, 6th day should start with unique dialogue with Lily resulting in you using a jar on her.