What's your headcanon for the "vampire incident" mentioned in Perfect Memento in Strict Sense? Presumably, between the windows and pc-98 era games, there was an incident where some vampire(probably Remilia?) came into Gensokyo, amassed a a lot of followers, and went on a rampage. A powerful youkai defeated the vampire and the spell card rules were formed. Another thing mentioned is the "devil's contract", which was formed when vampires first appeared. It prevents vampires(and other youkai?) from eating human residents. Whether or not these occurences are the same is unclear. There's a lot of other details that are left vague too. What do you think?