I've tried to start the Moriya sidequest according to the walkthrough on the wiki. I did chose the proper option after defeating Cirno so it should be available. I found the switch, but when pressing it, the last two sentences in the conversation appear in Chinese, untranslated, and I can't seem to enter the well after that. Does that mean the quest is not available if you try doing it too late?
According to the walkthrough you need to do all sidequest to get the true ending, so I'm worried. Yet, it didn't say anything about doing the quest immediately, and I'm already at mission 9 and lv 56 so restarting is not an option.
Also, does anyone know a better place for hunting Starfish Rock than Eientei?