The number one form of communication in "Sly and Single Again" is eavesdropping. Most of the important plot points shared between characters this episode were accidentally overheard and observed. It has happened quite a bit before as well, but this episode had an abundance of eavesdroppers.
Jung-woo is the primary eavesdropper, which makes sense because he tends to stalk Ae-ra in a fashion that could become creepy. He overheard that she miscarried during their marriage and that jerks him into an entirely new understanding of Ae-ra, her anger, her pain and their divorce. While I appreciate the fact that Jung-woo grows because of what he's overheard, it would've been better had he heard it directly from Ae-ra. Part of their marriage issues were the secrets and unilateral decisions. If they can overcome that, perhaps they can be together again