A control device includes a processor which: obtains first region information indicating a first region; obtains first position information indicating the position of an unmanned aerial vehicle tethered to a tethering device using a tether; and controls the tethering device using the first region information and the first position information to cause the tether to have tension corresponding to a specified distance which is at least one of the shortest distance between a boundary of the first region and the position of the unmanned aerial vehicle and a distance included in a predetermined range from the shortest distance.