Chu Sangwoo, a computer science student, is an uncompromising creature of habit who follows a meticulously organized schedule, drinks the same coffee every day, and sits in the same spot in each class. Tasked with doing a group assignment alongside freeloaders, Sangwoo decides that it is only logical not to credit them. However, his strict treatment causes his popular senior Jang Jaeyoung to lose the opportunity to graduate and study abroad. Seeing as he did nothing wrong, Sangwoo avoids Jaeyoung's constant phone calls. As fate would have it, the two men meet when Sangwoo needs a new graphic designer for the 2D game he is making. Jaeyoung is known for his charming personality, but he actually hides a hot temper. Despite his unchanging situation, Jaeyoung cannot stand Sangwoo's apathetic attitude and decides to get revenge by interrupting everything Sangwoo spent years carefully planning. Sangwoo tries his best to keep his calm, but Jaeyoung's presence and attractive smile may prove to be more than just a bug in his perfectly coded life.