I honestly think he might be happier with that ending, during the time he was in the duke's family he had to kept listening to his sister and his family basically didn't respect his wishes at all. I love him but he's a baby and he's too gentle, if he were to remain a duke there would be many people who wants to use him
somewhat spoiler.
i actually laughed at the fact that oscar almost became non-existent but re-appeared only after the whole treason that his sister had committed. (i can't believe that the people in the story describes isis as someone who is intelligent but clearly not, as she proves how idiotic she was on the chapters leading up to her treason)

I heard that crown prince and Aria is going to marry.And I'm really curious about what is going to happen to Oscar.He is such a kind and pure boi :< I hope he will be happy in the future UwU