She's Shibaki's mom, and yeah, he's genuinely terrified of her. She's got a serious yandere streak—the kind that involves actual knives and threats. Not exactly a warm parenting style.
There's also some pretty heavy subtext suggesting she's got some kind of twisted, possessive thing going on with her son that goes beyond normal motherly affection. Fans have picked up on what amounts to a reverse Oedipus complex situation, which makes the dynamic even more uncomfortable than it already is.
Content compiled by AnimeList.moe from publicly available sources.
