Vol. 4 ch 4.
I wasn't sure how I felt about this to start but I think that it get's better over time. Things start off very dubious but the characters have a ton of depth and there's a feeling of steady progression as well as they come to know each other. Things mellow out as they go along which seems kind of weird but sort of makes sense since they're operating on attraction initially and it takes a while to turn into actual care.
I'm not usually a fan of characters that have a sadistic streak but it's so well handled- there's a kind of childish innocence that can come along with being so easily delighted and also an insight-fullness that can be used for good that I practically never see that is utilized so well here. I honestly might end up giving it that last star because the writing is so solid, even though it's not to my tastes.
Oni to Tengoku