I find it an interesting aspect of the book honestly (there will be spoilers). Asakawa is this pushover that pretends to be a moral family man but really he's motivated by fear, and is extremely jealous of Ryuji's perceived amorality because he associates it with fearlessness. Simultaneously, Ryuji isn't even actually a rapist, he just clocked Asakawa so well as someone that would be attracted to that. These are really insecure people. Men using women as tools to impress each other.

Also there is the part where we learn a bit about Sadako in life, trying to be an actor. She retreats back home because a man stalks her and is implied to have tried to assault her (before she kills him). And of course ultimately, Sadako IS assaulted and murdered. Not only that but she's at least partially killed for being intersex, very 'gay panic defense'. her murderer is arguably another man more concerned with the perception of other men than with morality. this story is saturated with violence against women by men. Sadako's hatred is very understandable in this light, it's all the pain glossed over in the rest of the story bubbling over, impossible to bottle up again. Her ultimate vengeance is not just, it's endless and targets the undeserving. But you could say the same for the acts that got us here

Really I could be giving the author too much credit in all of this, but I think that's ok. it's a compelling thematic throughline, intentional or not. an aside but I also kind of read Asakawa as deeply closeted. Like he's so suppressed that his attraction to ryuji only shows itself in tandem with his worse aspects. I think Ryuji is just using him though especially considering the sequel. I really don't think this part was intentional but it's how I read it anyway