Wow. I didn't expect to feel so disgusted and appalled, not by the plot twist, but rather how this garbage plot made it to the release and even adapted to multiple media. It is also rated close to 9 here, it says alot about the majority of audiences not being able to tell what's so wrong about this. And I thought all these society narrative about incel and women rather be with a bear in the forest was an exaggeration.
I hope they handled it better in LN, i think it's fine if they wanted to establish that Oscar, being a teenager, didn't have the maturity to understand what he did, prank or not. His upbringing of being a prince with a lot of power explains his action pretty well. Regardless how hard he work, it doesn't mean he has that emotional maturity, and they can go through an arc about this for his character development.