Lee Seung-jae loves a women living in a next door, So-hee and sends letter to her, since he is a post officer. However, So-hee leaves her house for a new love and Seung-jae stops sending her letter to go to Mars.

Two friends - Min-gyu, a wild-animal vet, and Eun-hae, a fashion photographer - commiserate with each other when each realizes that the person they love is no longer in love with them. In anger, Eun-hae smashes up her boyfriend's car; in frustration, Min-gyu breaks glasses and carves up a spider. Min-gyu and Eun-hae each urge the other to be calm, to move on, to forget about it. Good advice, if only they could take it. "Why do humans need love?," these friends ask each other. Can jealousy, anger, and desire for revenge lead two jilted lovers to embrace what they have? Will someone dream of a giraffe?

The future Seoul, a city with the worst environmental pollution and the highest living prices. Shin-dong, the protagonist of the film, is helplessly living a repetitive and monotonous life, and is forced to find a new place to rent immediately by his landlord's unilateral notice. Unable to afford to move, his friend tells him that renting out a part of the house will complicate his rights and making it impossible for the landlord to evict him. Encouraged by his friend's advice, Shin-dong puts up an ad for rent. And when a strange newlywed couple shows up who want to live in the bathroom, Shin-dong impulsively invites them in.