Jin Mori is on his way to the preliminary for the martial arts tournament when he ends up chasing a snatcher; in the midst of his pursuit, he meets Han Daewi and Yoo Mira, two other high school students on their way to participate in the preliminary.

Mori, Daewi and Mirahave make it through the first round; with the next round coming up, the three of them talk about their reasons for entering the tournament; on the day of the tournament, Kang Manseok faces off against tai chi user Go Gamdo.

Mira faces off against WWD women's pro wrestler Mah Miseon, but she can't keep up; Mori faces the risk of being disqualified from the tournament after interfering with the match between Gang Manseok and Go Gamdo.

Mira is suddenly approached by businessman Oh Seongjin with a marriage proposal; she agrees to marry him in exchange for his promise to restore her family's dojo but marrying him means she must withdraw from the tournament.

Daewi shows no mercy in his fight against Mira with the goal of getting the money to help his friend who suffers from an incurable disease; Mori defeats Brazilian jiu-jitsu user Byeon Jaehee but is angered by Daewi's method of defeating Mira.

The tournament is a battle between teams formed from the top three participants; Mira wins the battle for third place; Mujin explains to the other administrators that this is all part of the search for the one with the potential to be the "Key."