A controller for a master work vehicle, includes a wireless circuit, an acquisition circuit, a message generation circuit, and a display control circuit. The wireless circuit is to receive, from a slave work vehicle configured to travel automatically, first information indicating a state of work travel of the slave work vehicle. The master work vehicle is configured to work in cooperation with the slave work vehicle. The acquisition circuit is configured to acquire second information indicating a state of work travel of the master work vehicle. The message generation circuit is configured to generate a first message based on the first information and a second message based on the second information. The display control circuit is configured to control a display to display the first message and the second message.
