Sweet Lies (K-Movie) (2008)

TV writer Ji-ho has been secretly in love with the same man for 10 years. After a night of binge-drinking, she wakes up to face the worst day of her life. She wakes up to find out she got fired for low viewer ratings. Her bag gets snatched on the way home and while pursuing the snatcher, she gets hit by a car. But the chain of unfortunate events turned out to be God-sent present. The man who hit her with the car turns out to be the very man she’s been in love with all these years. After bumping her head on the car, she pretends that she doesn’t remember anything and Min-woo is left with no choice but to bring her back home with him. Ji-ho’s childhood friend Dong-sik is worried as Ji-ho doesn’t come home for two days. He goes out on search and miraculously finds her and brings back her home. After learning that Ji-ho is suffering from amnesia after the accident, Dong-sik is determined to help her get her memories back.

(In the preview, basically she keeps faking her memory loss, asking, “Who… am I?” and then “Who are you?” to friends and co-workers. Jo Han-seon at one point says he’s Park Jin-hee’s boyfriend — probably lying to force her to admit SHE’s lying — and the confusion/hilarity ensues.)