Jung Soojung and Jung Krystal are twins.

Soojung is a caring but quite girl. She's really nice to all people who close to her.
People will think she's a cold person because they don't know her well.

Krystal is different with Soojung. She's an easygoing one. She has many friends while Soojung has not many as her because her quite type. But all Krystal's friends are Soojung's friends too.

Kim Myungsoo is the twins' childhood friend, cold but caring. His father is the twins' father bestfriend.
When he was a little boy he once comforted one of the Jung's twins because she fell down from a tree. Until now he still think that, the one he helped that time was Krystal, and he loves her so much and already got her first kiss.
But when he knows the truth .........

Kang Minhyuk, caring and funny, is the twins' best boy friend since junior high school. He close to both of them but only love one of them, and gave his first kiss to her. Who is she?