The Password Is 002! summary:

Sujung finally makes up her mind to confess her feelings for Dojin, her classmate who she's had a crush on for 6 months. However, Dojin is unable to recognize Sujung on the street and passes by her. Shocked by this, Sujung is unable to go to class and runs off to the gym's storage. There, she meets Jaehyun, who promises to help Sujung and Dojin get closer... How? By making a grand scheme to seduce her crush with his younger brother!