The drama begins with a scene where Gong Ju (Chun Woo hee) faces a crowd of slanderous adults as she tells them she did nothing wrong. The setting shifts to her teacher at the current school, Lee Nan (Jo Dae Hee), helping her pack her luggage as she is about to be transferred to another school in another town. When they ate lunch, he told her that it was not her fault but to wait for the results of the trial before deciding what to do next and not answering any phone calls. Lee managed to make her school transition as smooth as possible even though it was mid-term. Then, he took Gong Ju to the convenience store owned by his mother, Mrs. Cho, so that he could stay in her home. At first the mother refused but finally allowed her to stay. One day at school, Gong Ju was walking down the hallway and his friends through the classroom window, where a small group of girls were rehearsing a cappella song. When the leader, Eun Hee (Jung In Sung), sees her, she quickly leaves and remembers her friend Hwa Ok (Kim So Young). Another flashback scene occurs when Gong Ju is working as a cashier at a convenience store when a friend / classmate and the shop owner's son, Dong yoon (Choi Yong Jun), walks in and gets beaten. when he took some food and went back to see his friends. In the present, Gong Ju goes to swimming lessons and meets Eun Hee, who is trying to befriend her after hearing her sing in the dressing room. Eun Hee suggested that Gong Ju join a cappella group. Although not interested, Gong Ju asked Eun Hee to lend her phone to show the way to help her find her mother. They took the bus and Gong Ju went to her mother's workplace but in the end, she was rejected and fired. Angry, Gong Ju forcefully kisses and bites his mother's boyfriend before running away. Gong Ju stops by the drum music room at school and starts singing when Eun Hee and her friends hear it. Slowly, she begins to open up to the girls and tells them that her goal is to learn to swim at least 25 meters. Gong Ju's friends decided to post videos of her singing and details about her on the Internet so she could start a fan club, but upon hearing this, Gong Ju became angry. and ask them to delete the video immediately. Her friends were confused by her reaction and an argument broke out. Immediately after, a group of angry parents broke in and stopped the classroom to harass Gong Ju for throwing their son in jail. Gong Ju escapes and hides in an empty room. Another flashback was shown when Hwa Ok was gang-raped in Gong-Ju's house. Before that, Gong Ju went to her house, where Dong Yoon, Hwa Ok and at least 15 boys were hanging out and drinking. Dong Yoon was bullied by his friends. Although Gong Ju did not drink alcohol, Dong Yoon insisted that she drank a beer without her knowledge, was drugged. Gong Ju grabs a drink as Dong Yoon reassures the boys will leave if she does. Under the influence of the drug, she was also subjected to gang rape. The "party" ended when Dong Yoon's father arrived and took Dong Yoon, who had just raped one of the girls home; His father noticed but ignored that other girls were currently being raped. Shortly after, Hwa Ok committed suicide by jumping off the bridge. The scene goes back to the present where Gong Ju is sitting with the principal as he advised her that he would discuss the situation with the board, not knowing about her past. Ms. Cho's boyfriend suspects her innocence and urges her to kick Gong Ju out of the house but Gong Ju is ready to leave, after telling them that Hwa Ok is pregnant but she does nothing to help her. Gong Ju's friends at school found out about the rape, they texted her asking where she was and said it wasn't her fault. Meanwhile, Gong Ju is seen walking towards a bridge where she jumped into the water and drowned; an underwater silhouette was then shown swimming away, swimming much more bravely than she had ever managed. A background voice rang out asking Gong Ju why she wanted to swim so badly. Gong Ju's answer was "In case I want to start over because my mindset can change." when her friends chanted and cheered on her name.
Chun Woo-hee as Han Gong-ju Jung In-sun as Eun-hee Kim So-young as Hwa-ok Lee Young-lan as Ms. Cho Kwon Beom-taek as Police substation chief Jo Dae-hee as Lee Nan-do Choi Yong-jun as Dong-yoon Kim Hyun-joon as Min-ho Yoo Seung-mok as Gong-ju's father Sung Yeo-jin as Gong-ju's mother Kim Jung-suk as New husband of Gong-ju's mother Son Seul-gi as Min-suh Lee Chung-hee (actor) as Chung-hee Kim Ye-won as Ye-won Lee Ja-yeon as Ja-yeon Ha Jeong-hee as Homeroom teacher Im Dong-seok as Dong-yoon's father Min Kyung-jin as Principal