Disclosed herein is a sensor system that detects a stylus on at least one panel surface having an effective region. The sensor system includes a memory device including computer-executable instructions, and a processor. The processor, when loaded with the computer-executable instructions, performs: and obtaining a position of the stylus and a pen pressure value indicating a pressure applied to a pen tip of the stylus; outputting the position and the pen pressure value to a host processor. In response to the position being outside the effective region, the processor performs processing to conceal from the host processor occurrence of at least one of a pen-down indicating the stylus contacting the panel surface and a pen-up indicating the stylus being removed from the panel surface.