I feel really Sorry for all three lead cast members for being part of this Nonsense thing
Many people find ending disappointing because it was claimed loved but was actually a compromise. Woori
Woori feel something missing in her relationship and that was Love from her side, Only kang jae loved her in there whole relation
then she got pregnant and male lead enter into her life
she feel attracted to charming playboy with lot of money and fancy car, so she somehow blamed her boyfriend and brake up with him,
then holy Woori give her First kiss to playboy which she was saving from her boyfriend kang jae because she never loved her boyfriend enough to give up her church teachings but for our playboy she will do anything
that shows she love playboy and he is her first love and first kiss
kang jae was her loyal Dog they even said that he is loyal so she choose him not because she love him
and playboy will be allowed to enter there home whenever he want because he is father of child so she will be kissing and sleeping with her lover with her husband knowing and staying there as a loyal dog

From kang jae side he is cheated and will be cheated all his life and he accepted it like a idiot, she never tell him that she kissed other guy then she come back to him married him because he is loyal
if they wanted her to end with kang jae then they should have not made her date other guy or they should have had 20 or 24 episode to make it real that she realize she love kang jae only,
her love for kang jae which we never see is not believable but the way she acted toward playboy shows she loves him more