While I understand that Vio was a crazy psychopath stalker who harassed and later tried to kill her younger sister in the first timeline, I still don't like the prince. At all. I'm never going to get over the fact that, after the time reversal, the prince immediately assumed that Vio was behind the tea being poured on Maryjun. According to the timeline, that happened shortly after Maryjun had just arrived, meaning there would be no history of Vio bullying her younger sister at all. The only thing Vio would've been guilty of at that point would be that one year of "stalking" the prince (not sure if that's the right word to use. Will have to reread to be sure). There would've been no reason to believe Vio was behind that incident at all as it's completely unrelated to her only questionable action up to that point.
I'm glad that Yulan was introduced in chapter one and technically introduced before the prince (first timeline notwithstanding) as this gives me hope that he's the true ML. Had he been introduced in a later chapter or didn't play any significant role in the first one, I would've already given up on this manga by this point.
Btw, I'm guessing the reason why Yulan wasn't really mentioned in the first timeline was because he couldn't step in to defend Vio since she actually was guilty of all the things she was confronted about. This time, however, he could step in because she was actually innocent this time around. I like this as it shows that while he cares about Vio and will protect her from false accusations, he also won't condone her actual crimes and allow her to suffer the consequences. In other words, he's not just some simp who'll be on her side no matter what horrible things she does. Pure speculation, of course, but that's what I thought while reading this manga.