Satou's Aunt
さとうの叔母
A relative of Satou who had taken full custody of her after her parents died many years ago. There’s a possible chance that she may have been killed by her own niece since she’s rarely ever shown in person and is mostly shown in flashback sequences when Satou was a child; she is basically the one responsible for making Satou the deranged psychopath that she is today.