@Garlyle The prince is acting this way out of 'guilt'. He's not doing it out of 'love'. If she tells him to leave some distance and get someone else, he'll listen cause he doesn't want to have more guilt by doing something she doesn't want. The prince is an idiot, but he's not mentally disabled. He's not so dumb as to literally do the opposite of what he is told. And the reason the prince is even acting this way is because Aria is showing -zero- signs of independence. Yes the prince is at fault for essentially kidnapping her and Sei, but this chapter proved his reaction is again, based on guilt. As Lukcluck said, Aria is a -willing- victim of circumstance at this point, she is -willingly- rolling around in her own sorrow and letting the prince baby her. She is making zero effort to try and change things or get out of it.
So while it's both the prince and Aria's fault, let's compare their motivations. The prince is doing what he thinks is the responsible thing to do, because he feels guilt. Aria is wallowing around in her own self pity. So which of those two would you tell to shape up? The one who is in their head doing the right thing, but executing wrong? Or the one making no effort to do what's right even after being told they're causing problems?
The prince is by no means right or blameless, but at least his fault is only that he's stupid, and not that he is intentionally being a problem.
@shinsenryuu I was thinking that too, but then it hit me, the prince looks like he's kinda being overwhelmed by guilt, so I'm thinking he's actually running away from Sei, so he doesn't have to deal with the guilt of screwing them both over, instead of just one person.