Hmm, I personally do think he was mad she didn’t appreciate his sacrifice, and canonically, he was distraught that he would never be able to marry her. Whether this turned into “i hate Rize for not loving me back” is up for personal interpretation, I suppose.
I agree with the rest of your statement though – Furuta’s motives for kidnapping her were probably more complex than simply revenge (Lol when is Furuta ever simple). He almost certainly realized she was doomed due to her lack of self-control, so he decided to use her instead of letting his father have her.
Which is…cool morally gray motivation, but still wrong. Because despite her actions, Rize is not at fault for how the Washuus acted. And Furuta could have, you know, tried to intervene again. Tried to find some alternative that didn’t involve imprisoning, starving, and harvesting her for his plan. 😦
Thank you for your thoughts! I like this theory a lot. ❤