Twelve men were sent to a peaceful and different country for their vacation. Though the idea of still having one bodyguard is against their will, they still took the offer. It's quite rare to have vacation if you're an idol, so why not take the opportunity? What the staff didn't bother telling them is that their bodyguard isn't a grown up man with a family. But instead a girl their age who has quite left a strong impression to them. 

(picture not mine; source internet)