orologio en CB01 OFFICIAL. A high school freshman, Mi-ran, trips on the rope while practicing group jump roping for the school field day. Mi-ran’s novice homeroom teacher, Chae-young, replaces Mir-ran with another student, and Mi-ran feels confused. The next day, Mi-ran trips on the rope again. After arguing with Chae-young, Mi-ran makes a decision that can never be reversed.