The scar that was left on Kim So Hyun's body before she was missing in action. In "Who are You: School 2015" the secret was finally revealed.

On the 7th episode of KBS 2TV Monday/Tuesday drama "Who are You: School 2015" (script Kim Min Jung, Yim Ye Jin, director Baek Sang Hoon, Kim Sung Yoon) broadcast on May 18th, Eun Bi (played by Kim So Hyun) found out about the past of Eun Byul.

Eun Bi who was going through Eun Byul's cell phone met with Eun Byul's former friend Mi Joo. The number that was on Eun Byul's phone was none other than Mi Joo's. Mi Joo who met Eun Bi said, "That night, you and I met" and explained the situation.

The reason that Mi Joo had called out Eun Byul was because there was a text message sent to Mi Joo's phone. Mi Joo suspected that Eun Byul had been playing with the cell phone. At this, Eun Byul said, "Why? Are you feeling guilty for some reason? Why did you do something so scary?" he said.

In addition, Eun Byul said, "I sent that message too. It's definitely what Soo In said." At the time, what had been tormeting Eun Byul was Soo In's welcoming. Eun Byul said, "Soo In keeps appearing. She keeps following me. I'm scared but I can't tell her to stop following. I just feel so bad."