Things I Don't Know About You

"You will regret this." Aspiring drama writer, Gamsa, breaks up with her long-term boyfriend, Jiho, thinking he's been romantically involved with Eungyeong. Despite Jiho's ominous warning, Gamsa tries to carry on with her normal life. ...Until she hears Jiho and Eungyeong have been found dead together in a motel.

After an aspiring drama writer finds out her boyfriend has been cheating, she tells him "you are going to regret this!"

Returning to her everyday life she is contacted by a Police detective who tells her that her ex-boyfriend and the woman he was having an affair with were found dead in a hotel in an apparent suicide.

Soon other strange things start happening