Let's chill for a second here and think about what happened... Yuzuriha-senapi said that we should stop chasing the girl of truth thingie and that there was only one person she could never see through... they somehow can reach the school like that and know what is happening inside of it... we know the sister loved someone once before she turned fully to faith... Sion is still a mystery... Mayuri is being kept by someone inside of the school probably... they have been showing us Rikka reading the diaries... we know there is a betrayal and i think it could be not the one we went through... i feel like i should be capable of building a theory with all of that... for now... i think there is a character that is not shown yet to us... she could be the one holding Mayuri... she could be doing all of that and the Sister can't stop her... or it could be the sister herself... my brain hurt... because it could go anywhere... but i think i can reach a conclusion ,_,