Getting fired from her job as a reporter and finding out her brother was murdered in one day, Yoona couldn't be more broken. She seeks justice as she teams up with her best friend and detective, Sooyoung. They meet Seohyun along the way who has a mysterious personality.

Seohyun is a sweet, caring, loving and cheerful girlfriend, until Yoona noticed she began to change. She suddenly got distant, sensitive and always moody. She thinks she's cheating that she started following  her with the help of her friends whenever she leaves their apartment... which leaves them in discovering her secrets.

Sooyoung is Seohyun's best friend that do vlogs every time she's in the mood. On the day of Christmas, she suddenly thought of featuring her best friend on her vlog and the latter couldn't say no to it.