There are some unusual things about Goyo Cafe. Number one, their coffee sucks. Number two, your customers never order things from the menu. And number three, Yohan, the cafeteria manager, is deaf. So when Soohwa starts working there, even though they don't expect him to learn how to make good coffee, they ask him to expand his sign language vocabulary beyond "payment," "better," and "please." But when Yohan offers private lessons, Soohwa hesitates. Not because he doesn't want to study, but because of certain "problems" that occur when he hears his voice.