The main character in "Summer Time", Sang-ho, confesses to being only a minor participant in the incident, but he is nevertheless on the run. Seeking shelter in a small town in the countryside, Sang-ho (Su-yeong Ryu) ends up on the second floor of a boarding house. Hiding and biding his time until things cool down enough in the cities for him to return, Sang-ho discovers the married couple living underneath him and their odd relationship, all visible through holes in the floorboards.

Although the husband treats the wife as if she's a prisoner and padlocks the apartment whenever he leaves for work, the wife doesn't seem especially resentful of the situation. Being that he's a young man with raging hormones, Sang-ho easily becomes entranced with the beautiful wife. (The movie never introduces the husband and wife by name; even Sang-ho's name is not revealed until much later in the film.) Sang-ho becomes so aroused by the couple's daily couplings that he uses a stroke of luck (the husband loses his padlock key) to sneak into the apartment and make love to the wife. (The wife normally has her back turned during sex.) But even when the wife discovers Sang-ho's identity, she doesn't push him away; instead, the two begin a steamy affair.