I just finished it earlier at 3AM. This drama is not what I expected, in a really good way.
Now I'm shookt there are so many ending theories; understandable since the ending doesn't really give much hints on how things turned out for Heedo and Yijin after the break up especially in 2009.
I personally think they didn't get back together and Yijin is not Minchae's dad.
I love the series so much, so many great dialogues!