Song Jin Woo has worked as a non-permanent contract employee for the past 4 years at Moojin Girls' High School. He is a good teacher and dreams of a school where no one is left out. New contract teacher, Yoo Sung Pil, comes to Moojin Girls' High School. When Song Jin Woo was a high school student, he was bullied by Yoo Sung Pil and other students.

The Reason Not to Confess tells the story of Ji Hoo and Yoon Chan, who met in a college club, they both like each other, but didn't confess until 7 years later.