Park Somin was happy with her simple life. Kim Jongin didn't appreciate the wealth he was born into. A disastrous accident rams them into one another's new fate at seemingly the wrong time. But life doesn't always work in our favor, and neither do people's emotions. 

For Song Hyemi, Mafia was just a game played with friends in class. But once a joke goes too far, she ends up in a taboo relationship with Choi Seunghyun and the world of organized crime becomes her new reality. And of course, there is the manic Wu Yifan who loves to mess it all up. 

Minhee and Mark grew up as best friends. Once they entered middle school, the two started drifting until they were strangers. Then one random day during their final year of high school, their parents decided to arrange a marriage between the two.

Lee Jieun and Bae Joohyun were an inseparate pair. That is until one day autumn day Joohyun goes missing, causing Jieun to turn to her best friend's cousin Yoongi for help in finding her. 

Chaewon spends her school year in a little fishing town at her grandma’s house. But one semester she returns to find Jackson sleeping in her bed.