Yeon Shi-eun, a diligent student, faces bullying from Jeon Young-bin, a troublemaker. Young-bin escalates his harassment, pushing Shi-eun to his limits, leading to a confrontation between the two characters over Young-bin's behavior.

Although he earns a fearsome reputation, Yeon Shi-eun's stand doesn't have the desired effect and Jeon Young-bin doubles down. A remorseful Oh Beom-seok plucks up his courage and takes responsibility for his actions.

Gil-soo's boys get beaten up, he demands 15 million won from Shi-eun, Beom-seok, and Soo-ho within three days. Shi-eun seeks Young's advice and information about Gil-soo to resolve the situation.

Shi-eun sees Soo-ho's blood on the floor and calls Young Yi for help. Gil-soo tells Seok-dae to come, so Young Yi follows him with her GPS tracking app on. Meanwhile, Soo-ho and Beom-seok are tied up by Gil-soo's gang.

While hanging out in a karaoke room with his friends, Beom-seok runs into the bullies from his previous school. Soo-ho makes them apologize, but Beom-seok isn't happy with Soo-ho ordering him around. Shi-eun becomes more worried about Beom-seok who seems to be getting more unstable.

Beom-seok befriends with Jung Chan and Tae Hoon, he reeks of alcohol every day. Shi-eun thinks Beom-seok is being used by Jung Chan and Tae Hoon. He also thinks Beom-seok is behaving that way because he is lonely. Shi-eun wants to help Beom-seok, but Soo-ho thinks he's done enough. Meanwhile, Beom-seok pays Woo Young to beat Soo-ho on his birthday.

Shi-eun gets beaten up by the guys Beom-seok paid to beat up Soo-ho. Shi-eun gets seriously injured, but he doesn't tell Soo-ho about it to protect Beom-seok. Soo-ho finds out later and decides to confront Beom-seok. Beom-seok pays Woo Young again to beat up Soo-ho.

Shi-eun and Young Yi get anxious as they can't get hold of Soo-ho for too long. After Shi-eun finishes his exams, he hears the shocking news. Meanwhile, Beom-seok's dad tries to make Beom-seok go study abroad.