Umineko: When They Cry - Season 1 Episode 13 Gambit

Rosa recounts how she met the human Beatrice confined in a hidden mansion, Kuwadorian, on the island twenty years ago and helped her escape, only to see her accidentally fall off a cliff to her death. Beatrice confirms to Battler that she truly died as a human, and that there are currently no more than 18 people on the island, forcing Battler to accept his loved ones as possible culprits. Genji, Shannon, and Kanon are later summoned to Kinzo's study, where they see Beatrice offer him as a sacrifice and kill him. Kanon is pit against the seven Sisters of Purgatory, defeating Lucifer in a duel, though he and Shannon are overwhelmed as they try to fend them all off at once, prompting Genji to euthanize Shannon and Kanon before he is put to rest by Ronove. The Sisters search the mansion for more sacrifices, killing Gohda in the process. They find Kumasawa as well, who claims to have been waiting for Beatrice. Beatrice reveals Kumasawa to be her predecessor and teacher, the former Beatrice.