Poor Kahi was in charge of training the difficult 'F Group' in dance on the January 29 broadcast of Mnet's survival program, 'Produce 101.'

On this day, they had to master the dance to the song "Pick Me" with the help of instructor Kahi, who was a well-known backup dancer even before her rise to fame as an idol.  As Ariyoshi Risa was unable to do the steps properly, Kahi could not hide her unhappy expression.  

SEE ALSO: "This is a national shame," K-netizens react to TMZ's headline on the Kim Soo Hyun controversy

As they continued, Kim So Hye messed up the moves, so Kahi said, "What do I do about this?" looking deep in thought.  Kim So Hye seemed upset herself as she said, "I feel sorry toward the others because it seems like only I'm messing up."  Despite her sweet thoughts, she continued to mess up.

Kahi finally said, "This is upsetting.  It doesn't look like you're working hard.  If you continue on like this, you can only do backup on stage."