CONTROLLER, CONTROL METHOD, AND BRAKE SYSTEM

The invention obtains a controller and a control method capable of improving safety by an automatic deceleration operation while preventing a motorcycle from falling over. The invention also obtains a brake system that includes such a controller. In the controller, the control method, and the brake system according to the invention, a control mode is initiated in response to trigger information that is generated in accordance with peripheral environment of the motorcycle, and the control mode makes the motorcycle, which includes a damping device damping kinetic energy, execute the automatic deceleration operation. In the control mode, the automatic deceleration operation is executed in a state where a damping rate of the damping device is increased to be higher than that immediately before initiation of the control mode.