The day of the World Triathlon Cup Tongyeong has finally arrived! The first event of swimming begins with tension. Will Seo Yeon, who has a fear of water, be able to finish the course in 50 minutes? In the second event of cycling, Uie is faced with an unexpected situation and bursts into tears. As soon as Ju Hyun starts cycling, the chain comes off, and she has a mental breakdown. Sports Genius In Ah, who successfully completed swimming and cycling, complains of knee pain while running. How will Iron Girls’ 120-day journey toward the completion of the triathlon end?