In a world devastated by a fine dust pollution, society has been divided into two castes: the "Cs" (Clean) are those who can afford a vaccine at birth which permits a 100-year lifespan and the "Ns" (Non-clean) are those who can't and will usually die by the time they are 30. Two young women who share the same tragic fate take comfort in each other's company.

Ah-young, a grown orphan with government aid cut off, starts working as a nanny for Young-chae, a single mother who works at a bar to make ends meet.

Myeongjoon and Jeongho, high school students in Hwacheon, are old friends with different personalities. One day, Jeongho brings a new bike and Myeongjoon suspects him of dishonesty. The bike owner appears, but Jeongho has no intention of accepting Myeongjoon’s advice to return it. The shadow of catastrophe becomes clear in vague emotions.