Rui is the 'guardian' of this mansion. He can appear in human form, but prefers to sit in a locked room. He is a kind of spirit of this sekai, knows absolutely everything, but is silent. Often amenable to nastolgie. Quiet, does not show itself to other visitors, but 'saves' them from their fate. He doesn't know what it's like to open up to people. Doesn't understand what feelings are. In general, rather lonely, closed, but very kind. He has a collection of music boxes in his loked room.