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Seung Yoo and Ye Rin prepare in earnest for the Math Olympics. Jung Ah and Min Jun teach Ye Rin the means to win, and Yoon Su finds out about the corruption in the competition. However, Yoon Su goes to Jeju Island with Seung Yoo to help him with the contest. On the same day, Ye Rin arrives at Jeju Island for internship activities for the competition.
Lim Soo-jung
Ji Yoon-soo
Lee Do-hyun
Baek Seung-yoo
Jin Kyung
Noh Jung-ah
Woo Da-vi
Sung Ye-rin
Jang Hyun-sung
Sung Min-joon
Byeon Jung-su
Yoo Hye-mi
Choi Dae-hoon
Ryu Sung-jae
Baek Ji-won
Min Hee-seung
Kim Ho-jin
Baek Min-shik
Jeon Guk-hyang
Shin Kyung-in
Oh Hye-won
Noh Yeon-woo
Lee Kang-ji
Lee Hyun-jae
Kim Ji-young
Kim Ji-na
Oh Kwang-rok
Ji Hyun-wook
Han Gi-joong
Ryu Hyun-il
Choi Seung-hoon
Young Baek Min-jae
Jang Gwang
Noh In-Hyeong
Son Jin-hwan
Principal Oh Jin-taek
Jeon Jin-gi
Vice Principal Choi Sung-han
Yang Jo-a
Kim Jin-hee
Ahn Sang-woo
Han Myung-Jin
Choi Woo-sung
Jang Kyu-young
Lee Young-eun
Park So-jung