The leading lady here is the English-speaking girl in The Heirs. The lead is Rain of Full House fame.
I think the leading lady looked better in Heirs where she had no bangs. As for Rain, he looks better here than in FH where his hairstyle really annoyed me.
AM about to start watching Episode 4 (thanks, Susan for the recommendation) but thought of sharing a song the leading lady sang in Episode 3. Found the complete version in YouTube, but it has no subtitles. A pity really because the lyrics are quite moving.
I’m sharing the abbreviated version which was what the female lead sang in Episode 3. Oh, and I just checked: she’s Krystal. Per WIkipedia she belongs to the “South Korean girl group f(x) and the ballad group S.M. The Ballad”