A seat system includes a seat including a sensor configured to acquire information for detection of a motion of an occupant seated on a seat body, a terminal device configured to acquire the information from the sensor, and a server capable of communicating with the terminal device. The terminal device executes a game using the sensor based on the information, and acquires an execution result corresponding to the occupant for a game played by the occupant. The server generates integrated data by integrating execution results of the game acquired from another terminal device, and computes a reference value for execution results of the game based on the integrated data. The terminal device or the server assigns a difficulty level of the game for the terminal device based on the execution result corresponding to the occupant and the reference value. The terminal device reflects the difficulty level on the game.