Responses
Oh uhm spoiler
He's not being brainwashed, or so i think, he drank the tea Angela offers to him and it has love potion in the first timeline now that she heard the "prince" remember the earlier chapters in 2nd timeline? Yep, she were about to target Cassius but she changed her target to the prince so ye
I think Cassius must have been brainwashed. His eyes in the past life were very strange and even if he had fallen in love at first sight why didn't it happen this time too? The difference is that the target is the second prince, so she had no reason to struggle with Cassiel. Also, he seems to like Jayna a lot, is it possible to go from love to neglect in less than a day? At the very least he would have hesitated or felt bad for treating his childhood friend and fiancée like nothing (judging by the gentle, gentlemanly personality he's shown so far)
And all this witch talk and brainwashing is very suspicious, it makes me question even more. Well, if there was no brainwashing and it all happened naturally, then congratulations Cassiel you are an asshole