Managed to get what's identified as ending 2, but a bit lost on any others. Saw an Oni girl in the NW altar area, took Elemia to find the white ropers, helped the detective twice, and escorted pink hair through a dungeon when you infiltrate the cult. Think that's as far as I've gotten in any quest lines so far, not sure how to open up anything else.
EDIT: Poking holes in every place I could think of, I managed to hit the Vampire quest and clear it all the way to Ending 5. Also met Rita and got to the point where her scene is unlocked and you can have her join you. I feel like there's more to do with quests for pink hair, but I don't know where she is now.