I notice that at Korean sporting events, groups of fans will set a called cheer. So, what happens is a girl shouts out in cadence and calls for a cheer, then the fan group answers altogether with a cheer.
What is the cheer leader girl called?
At 6:05 of the following video, you can hear examples of the cheers. First you hear the cheer for the first contestant ("Jin Air FIGHTING !!!"), then a second similar cheer is given by the fans of the opposing team ("SKT FIGHTING !!!").