So FL's Daughter name is Kim Min Chae. I think ML change his surname to Kim. It might be his Mother's Surname but we don't know yet. Maybe he changed it because he doesn't want that Surname anymore or he doesn't want to be chased by those guys.

I think their love story might be sad. Perhaps, due to the financial problems of his family, they will not be able to be together? Maybe Na Hee Do's daughter's father will be her chat friend? Because she is probably not married, since her mother never gave her wedding rings? Or maybe Injeolmi (chat friend) is a girl, because the name means rice cake; possibly it may be this person's favorite delicacy?

I think baek yi jin changed his surname.

Kim Young Sun is Yi Jin mother's name, so Yi Jin will change his surname to his mother's maiden name, or Na Hee Do will meet someone with the same surname? @Shino, you are right :)

I am just putting it out there right now that Injeolmi the chat friend is Yi Jin given the 6 degrees of separation narrative arc in k dramas.

 Izyda:

I think their love story might be sad. Perhaps, due to the financial problems of his family, they will not be able to be together? Maybe Na Hee Do's daughter's father will be her chat friend? Because she is probably not married, since her mother never gave her wedding rings? Or maybe Injeolmi (chat friend) is a girl, because the name means rice cake; possibly it may be this person's favorite delicacy?

Same thoughts... I am thinking that their story will continue in the present times

 Izyda:

I'm not so sure if it's him. Then he'd be lying to Na Hee Do that he didn't know her. What about the Go Yu Rim issue, Hee Do wrote to her chat friend everything about it, if Yi Jin knew about it, wouldn't he explain her behavior or try to excuse her? Unless he don't want to get involved in their affairs. But when Hee Do said to him that he is cold and inaccessible as Go Yu Rim, he seemed surprised?     Or, you may be right, usually it is like that in dramaland :)

If it's him, i don't think he is lying actually. Remember they still don't know about each other yet. And all he has right now is just a guess. Because HD story looks similar to his chat body. And remember when he was trying to ask where she stays? Probably he might have had a feeling it's FL.