Spoiler: First, this has more chapters in With a strong-willed Marchioness, Prince Yandere's Love Offensive
and in there it was "explained" that he "hated" her because he didn't hate her but couldn't deal with his feelings for her and was jealous of her cousin who she seemed to have a good relationship with. And he was mad that originally lovestruck mc treated him nicely but after he had a fit of jealousy in childhood and acted like a bitch towards her for years and so when in adulthood she treated him in that mature not lovestruck way he made a surprise pikachu face AFTER MISTREATING HER FOR YEARS. And threw another hissy fit.
Their relationship is so fffnnn dumb in so many ways. The art is gorgeous, but the story is a trainwreck. Absolutely atrocious but pulls you in.
Wow wtf…thank you very much for the spoiler
Wtf is happening. She literally raped him and why does he hate her so much wtf