what i like about this story is always going to be that the central conflict is obscured by the "plot", and it is so easy to misunderstand what is goin on. Roa and Nocton were already broken long before Alice makes her accusation, which they both knew to some extent. Roa didn't want to be in an unequal relationship, nor did she want to be the pitiful duroa who clings to duke edgar despite him not wanting to marry her. Nocton dug his own grave with her a decade ago, and he knew he did so but not in the way he thought he did. Alice is a catalyst in two ways: getting roa to take a decisive step away from nocton by getting engaged with someone else, and of course forcing his secrets out in the "open".
every time i read the webtoon or the novel, i am always a step from losing it because the layers make the story so delicious. Is nocton at fault? sort of! he hurt roa repeatedly, and knowingly. Is roa at fault? also sort of! she approached him and continued to approach him for dubious reasons, and while she did fancy herself his friend for a while, a large part of their friendship was that she wanted to be safe. she let him hurt her for that reason.
everything was a mistake, indeed.