When Jo Gang-Ja attended high school, she was notorious for fighting. She gave birth to her daughter A-Ran in her late teens and became more responsible. Her daughter A-Ran is now a high school student, but A-Ran is bullied at school. Jo Gang-Ja decides to go back to high school to protect her daughter. Jo Gang-Ja becomes a high school student again.

After a surprise visit from her friend Geum-sun, Eun-sim is headed to her hometown with Geum-sun. There, she catches up with Tae-ho who had feelings for her when they were teenagers. Her long-lost memories come to life one by one.