When her best friend has to go abroad for a while, she asks the female lead to look after her younger brother. Little does she know that her friend's younger brother isn't a little kid, but a college junior. Believing that the female lead likes obedient, well-behaved guys, he puts on a plaid shirt and black-rimmed glasses and pretends to be a dull, well-behaved student to get close to her. In reality, a well-behaved, dull guy isn't her type at all. The female lead personally teaches him how to dress, groom himself, and make friends. As they spend more and more time together, she falls in love with the younger man. However, because he is her best friend's younger brother and there is an age gap between them, she has reservations about their relationship.