How do I obtain the first ending? I've gotten all 3 endings save for the first and I don't know if that would involve me incorrectly assessing all the dolls.
In order to get the 1st ending, you need to make at least one mistake! You can re-do a doll and mess it up on purpose. Then just continue, like usual, and the bad ending will happen!
Thank you for taking such an interest, that you managed to get all the other endings though!