Seventeen-year-old Nam Jayu has no friends—simply because she is too shy. She keeps to herself, overthinks everything, and is so quiet that people barely notice her. When the most popular boy in school, Yeo Jahyeok, lends Jayu his umbrella during a downpour, she is quickly put in a predicament: nothing is more difficult than finding the right moment to return the umbrella to the boy who is always surrounded by people.

Even though Jahyeok appears remarkably social thanks to his good looks and academic accomplishments, he is actually extremely introverted. School is but a prison to him, where people constantly approach him, never giving him room to breathe. As he struggles to make it through every day, something about his classmate Jayu's calm, quiet presence draws him in. Both of them need to exert themselves to engage with someone new, but once they do, they may discover something beautiful in the friendship between two hopeless introverts.