Jung Eun Bi, widely known for her stage name Eunha, is a South Korean singer who just debuted as the lead vocalist of the popular girl group Gfriend. She is a hopeless romantic who has been secretly in love to the oldest member of the nation's Bangtan Boys - Kim Seok Jin, but she has no courage of telling anyone or even confessing her feelings to him.

Jeon Jung Kook, the golden maknae of BTS, likes Sowon - Gfriend's leader. He admires her determination and leadership to her group, but he keep his feelings from everyone since he knew from the start that Jin likes her as well.

One day, Jin and Sowon finally announced to their groups that they dating, making Eunha and Jungkook's hearts shattered into pieces.

They found themselves crying secretly. To mend their broken hearts, they will play a game that will make their already problematic life even more problematic: dating each other for a hundred days.

"Let's date and let's see who can move on faster."