I think after she stripped him of all his clothes and isolated him from the rest of the world, it's clear that she's on the road towards some form of sexual abuse being the outcome. Keep in mind that sexual abuse is often about control or assert authority over someone close to you. Keep in mind that in his mother's mind, he betrayed her just like his father did and is losing the one aspect of himself that seperates him from the rest of his kind, which may ultimately lead to her raping him as a form of asserting that his lust (Or, in his mind, love) should only be directed towards her. It's almost like a Jocusta complex.
What makes me interested is I would want to see both how Yuri would react to this and Haru, because I think Yuri (even if I think she's been out of character) would see the consequences to her actions as a negative thing, as a punishment gone too far if she knew how his domestic life really was and so she would try to act how she views herself as, in that she is owed him because she sees him as a prize to be won. Haru, on the other hand, would most likely try to break him out or call for help, but knowing her, she would definitely try to take things into her own hands.
Potentially, it could be the most interesting if Yuri finds out about his situation and then tells Haru what has happened to Souta, which may force them to work together as allies. That would be quite the turn of events, and I would be interested to see where it would lead.