TV producers plan a ground-breaking entertainment program and come up with the concept of having forgotten female idols engage in battles. They host with the MMA(Mixed Martial Arts) YouTube channel a female idol fighting competition called “Girls in the Cage.” The winner will receive a prize of 100 million won and get to debut as a new idol group under the name “Girls in the Cage.” The journey of eight female idols as they battle their way to the top begins. Fierce competition starts, but in that process, competitors build friendship and gain something more valuable than the prize.