Too bad for the ending, I'm very disapointed.
I think Seo Jin Won is very unreasonable for her 2nd break up with Lee Seung Yo. She is not professional, and she is weak woman despite of adult age, she can't fight for her feeling and still very immature in relationship, she can't be model person.

Their relationship will won't work, because Seo Jin Won don't have faith, trust and loyalty to Lee Seung Yo. First she didn't spoke about her thoughts regarding the past relationship of Lee Seung Yo.
To have a successful relationship we have to clear our mind and removed any kind of doubts.
Seo Jin Won really don't had a love with Lee Seung Yo, her feeling toward Lee Seung Yo, is just curiosity, fear to be alone, and excitement.