Ok, I am really confused now!

[dangermousie]

Umm, why does the existence of a previously unknown about almost twenty year old kid whose mother is happily married to the kid's stepfather who raised him and who you've long gotten over, means Do Jin is breaking up with Yi Soo as it seems that somehow the fact that he didn't use protection (or did and it failed) two decades before he met her makes him unqualified to be her boyfriend or married to her or anything?! Wtf is this a Korean thing? Because whie this fact would certainly lead to a discussion within a relationship, how on earth this is grounds for dumping the woman you love due to unworthiness/inability to be her boyfriend?

I honestly don't get wtf Do Jin is thinking?