On the July 15 installment of 'Jessica & Krystal,' Krystal talked about her super busy schedule since her group f(x) made their comeback with "Red Light."

She said, "I sleep a maximum of three hours?  There was even a time I stayed up all night and then went to a music program.  It's been a long time since I've had a schedule everyday," considering it has been one year since the girls' comeback.  

"That's why I'm not used to it now and feel overwhelmed," she continued.  She then dished on how her sister, Jessica, was when she had no schedule: "My sister does not like moving.  She's always lying down.  On days with no schedules, she lies down and doesn't come out until the evening.  Our parents' athletic genes all came to me.  In the past, I only had strikes in bowling. Even for things like high jumps, I was number one a lot."