Jungsoo and Heechul ended everything between the two of them. They thought, if they would end everything, everything would be fine. Years passed, their lives were still going on as they planned.  Not until something happened that night. Guess they never really moved on from their past.  

Heejin and Chaewon meet each other.

Hyejoo gets a girlfriend and Chaewon gets impossibly jealous.   Choi Yerim had no right to waltz in and steal Hyejoo from her like that! Who did she think she was?   As Chaewon's best friend, Heejin is obligated to go with her on her spy missions to try to sabotage the new couple and listen to all her hate rants about Yerim.  

Heejin's world was dull before Chaewon entered her life.  or  the soulmate au where you don't see colour until you meet them. 

heejin finds some unexpected comfort