A touch sensor includes a sensor and a processor. The sensor detects touch operations on first, second, and third regions of a sensor region disposed along a longitudinal direction of an outer edge portion of a terminal device. The second and third regions are on opposite sides of the first region. The processor identifies the orientation of the terminal device as a first orientation where the sensor region is located at the top or bottom of the terminal device or a second orientation where the sensor region is located at the right or left of the terminal device, and makes a different determination as to whether the first region is depressed based on whether the identified orientation is the first or second orientation, in response to detection of the touch operation on at least one of the second and third regions together with the touch operation on the first region.