Soojung and Yonghoon spent a passionate night together that felt out of this world, but when they woke up in the morning, something was missing. They can't find the condom they should have used. They had sex four times, so why are there only three condoms? The panicked couple searches frantically for the missing condom, but there is no trace of it anywhere. In the end, they look at each other in confusion and begin to recall last night. Amid the unclear memories and confusion, even the slight romance they felt last night is about to disappear.