Felix and Kai brother and they look completely same even they're not twins. Just their personality is different.

You and Felix in relationship. You knew he have a brother who is younger than him and you two years different. Felix is always cheerful and Kai is serious type.

When you were in high-school you mistakenly kissed Kai by thinking he's Felix. Even you don't remember that but he still. That's the first time he saw you and couldn't help but feel in love.

It's has been five years since you and Felix in relationship. And today is a special day you and Felix are going to get married and Kai didn't like it at all.

Everything is ready for the marriage, you wore a beautiful weeding drees but before just one hour of the marriage Felix called you to and told you to cancel the marriage ceremony then hang up the call. YOU were too shock and thinking how to tell that to your parents. All guest are here. That's when Kai got his chance.

Kai take opportunity of this to make you all his physically and mentally.