Overweight nerdy engineer Jang-hyeok (Lee Woo-je) was admitted in a hospital because of Hepatitis B. His nurse in charge was cute and perky Da-eun (Chae Soo-bin). Hyeok liked Da-eun and would do various favors and errands for her during his admission. Afterwards, Da-eun also reciprocated the feelings and became his girlfriend. When Da-eun gifted him with a pair of running shoes, Hyeok promised he would lose weight to keep up with her.
Jang-hyeok (now played by Jang Ki-yong) did lose the weight, and was now a slim and handsome executive. He was promoted so he had to drive through horrendous traffic from his house with Da-eun in Incheon to his office in Seoul everyday. However, it turned out that the job required a lot of overtime, which he had to spend with his new partner Bo-yeong (Krystal Jung). This tough arrangement would lead to a difficult strain in his relationship with Da-eun.
The story was quite a typical story of a sweet love story turned sour, hence the descriptive title. Hyeok and Da-eun had a very good romantic relationship going. However, along with Hyeok's progress in self-confidence and career opportunities came challenges that he never expected would get in between him and Da-eun. Having limited experience on love, Hyeok had no idea how to handle things properly, causing the whole thing to teeter on the brink.
The way the scenes unfolded onscreen, that critical transition of old Jang-hyeok to the new Jang-hyeok was smoothly and logically done, raising no questions about the use of another actor. Chae Soo-bin had very good chemistry with both these actors who played Jang-hyeok, hence we were all rooting for their relationship. Krystal Jung's Bo-yeong was ruthlessly ambitious but boorish in behavior, so she was clearly painted as the antagonist.
However, by that climactic scene at the airport, this film was really all about how the director Lee Gye-byeok succeeded to fool us big time. He had just perpetrated one major case of cinematic prank, and we are all the willing victims. That major revelation can really be very annoying, especially if you had been seriously invested. But thanks to his storytelling skill and the actors' charms, we can still manage a wry smile at the deception we all fell for.
This review was originally published in the author's blog, "Fred Said."