Mark asked Jb out on a date on one particular day. Since Jb couldn't reject, he says yes but ended up making his twin brother, Jr, go on the date with Mark instead. Jr of course rejected, but Jb insisted because he knew that Jr had a major crush on Mark.

Just one day at a time is okay, go back to yesterday. And then... I want to go back to that time.  

Mark and Jinyoung have been dating smoothly for a year now. They had never once got into an argument, but things are about to get heated up when Mark's ex-girlfriend comes back.

December is supposed to be a month filled with happiness and joy. Unfortunately for me, it was a month full of sorrow.

Mark confessed to his best friend, Jinyoung, that he likes him many times. However, he's always getting rejected because Jinyoung doesn't want to be anything more than friends. So why is it that Jinyoung feels so uptight and annoyed when Mark told him he's going on a blind date?