I can't seem to trigger the mia / elise scenes. New game, at day 2, after meeting with rose, I can't go to diner room day or night whether I clicked the crystal or not on that save
Romancing Mia will block the Elise route, yes. There is no harem route planned, you will have to choose one of the girls, this is just first of the many future scenes that will work like that.
