Gyeong-su and Na-yeon got into a big fight,causing Na-yeon to get so frustrated,that she resorted to putting zombie blood on Gyeong-su's cut. Later on, as their teacher,that was in the room with them, tells Na-yeom to apologize to Gyeong-su. She grumbles a few words before she agrees, as they were all occupied with something, her eyes land on the broken stick, that has some zombie blood on it. She makes sure that no one is looking before she takes her handkerchief out. She wipes some zombie blood of the stick using her handkerchief. As Ms Park tells Na-yeon to apologize. She agrees, as she goes in the room, she just kept on throwing insults at Gyeong-su. But as Gyeong-su ignores her, Na-yeon grabs his hand that has a cut on it, and takes her handkerchief out of her pocket. She dabs the zombie blood thats on her handkerchief on to Gyeong-su's cut. Causing the zombie blood to mix with his. Making him get infected. As he gets infected, Cheong-san starts crying, as he gets on the window, he whistles the song that Gyeong-su would always do. As the infected Gyeong-su hears him, he runs after Cheong-san. Cheong-san grabs on the rope from outside the window and hold on to it, causing Gyeong-su to fall out the window and him to not. As he gets back inside the room, he breaks down.

As Nam-ra tells them what did Na-yeon do. Cheong-san gets angry, as he yells out insults, tears streams down his face, because he lost someone that he could not replace. Gyeong-su is his bestfriend. Later on, as Cheong-san is still upset, he starts punching the locker that was in the classroom. Ms Park stops him, before he injures himself even more. Later on, as On-jo sees Cheong-san staring out the window blankly. She speaks up,

"Are you okay?"

She say, her voice is full of concern. Her eyes drop to his knuckles, its bleeding, it has cuts. And she knows that the reason of it is because he started punching the lockers.

As Cheong-san hears her words, he ignores her, he thinks that he doesn't care, but she does, she really does.