We binged the entirety of this series today (12 episodes), which is based on a book by Yukito Ayatsuji, who is my wife’s favorite author (and I read his mystery novel The Decagon House Murders not too long ago). Ayatsuji is better known for his mystery novels, but this story is horror, although there’s certainly a mystery surrounding the whole affaire, which is capped with an ending I didn’t guess (same as Decagon). It’s a fantastic series, beautifully animated (while quite gruesome at certain points), with an opening theme song that is just insanely weird (and kinda suits the series). Highly recommended.