my theory is that Dae Oh is the dad, self centered actor liked her too so he never cleared their misunderstandings…
Given the four episodes, we have similar theory. I also think that Dae Oh is father. Ae Jong left Dae Oh because she saw Dae Oh with another women. And she only know that she is pregnant after they brake up. Ru Jin also loves Ae Jong. (I don't think he is a gay because he asked to Ae Jong that Ae Jong didn't consider for him). So he did something bad between them and although he know the reason of their misunderstanding, but he keeps quite. The teacher also loves her, so he will take responsibility and try to become a dad for Ae Jong's kid. However she left everyone and gave birth. Gangster is interested towards her because may be his late wife looks like Ae Jong.
I hope there is a big twist and unpredictable secret at the end, otherwise everyone can be a writer if the story is that simple.
I hope there is a big twist and unpredictable secret at the end, otherwise everyone can be a writer if the story is that simple.