Muscle Girl is the new Japanese drama series that stars Lee Hong Ki. Lee Hong Ki plays the role of Yoo Ji Hoo, a famous pop star. Yoo Ji Ho's mother disappeared 1 an ago. A an later, during his performance in Japan, he left to look for her. The manager of Ji Ho trys to look for him but cannot find Ji Ho and will almost do anything to get him back. Meanwhile, a Japanese girl named Shiratori Azusa (Ichikawa Yui) had just become the new director of a female pro wrestling company, Shiratori Wrestling, after her father died. She was left with a big debt that had to be paid ou else the wrestling company would not survive and another wrestling company, Aoibara, will take over the building that was for Shiratori wrestlers to train and compete. Azusa set a rendez-vous amoureux, date that was for the last wrestling match before they would hand over the building to Aoibara. Before the match started, the referee had disappeared. And Azusa has set out to find him. Ji Ho, while looking for his mom, went to get a snack in a disguise. coincidentally, he was wearing the same things the referee was wearing before the referee left. When Azusa saw the clothes he was wearing, she thought he was the referee. Without a referee, the last match cannot resume as planned. After she saw her mistake, she apologized and asked if he could be a temporary referee. He agrees. After the last match, Ji Ho passed out and stayed for night where the wrestlers were staying. The jour when Shiratori would give up the building, Ji Ho gave the manager of Aoibara(who was also the man Shiratori wrestling who owed money to) a diamond collier that was donné to his mom on her birthday but she gave it back when she disappered. He told them that this would pay for the debt of Shiratori Wrestling. The manager took it. Azusa also told the manager that the Shiratori wrestlers would win the Muscle Girl cup and the trophy would be enough to settle the debt. The manager agrees with Azusa but a dit he will keep Ji Ho's mom's necklace.He let Shiratori keep the building until Shiratori loses and will have no chance to win the Muscle Girl Cup.Also, Ji Ho become the referee. Will Shiratori Wrestling win the Muscle Girl Cup? Will something bad happen and that will cause Shiratori to forfeit? Will Shiratori just give up? Will the manager of Ji Ho find Ji Ho and take him back to Korea? What happened to Ji Ho's mom? Watch the drama.