I think he does. She was willing to not marrying him. So much so she told the grandfather she wouldn't marry him. But to try and steal his brothers fiancee is a bit shady.
Yoo ra is so annoying. Sumin is so much better at being the villain. Yoo ra comes off a little to unrealistic. More like a spoiled brat throwing a tantrum than anything else. That new story line is not working imo.