By chance, a man and a woman meet on the KTX train and spend 24 hours in the unfamiliar city of Busan, South Korea. Soo-Jung has been with her boyfriend for 10 years, but their romance is now nothing but a lukewarm relationship. The night before her business trip to Busan, she heard that her friend is getting married to her first love, and feels distracted. On the train to Busan, she sits next to Jae-Hyun, who’s claiming himself as an Agapemonite and that he willingly jumps into bed with a woman for one night. Falling for her gorgeous hips, he keeps coming on to her during the journey. She tries to push him away, but ends up sharing the car ride to Busan with him due to the sudden breakdown of the train. She begins to slowly open up to him as he consistently tries to win her heart. And as the time passes on the road, she gets to see the true inside of Jae-Hyun hidden behind his featheriness and finds herself attracted to him.