An input detection system includes a plurality of electrodes arrayed in a detection region, and an input support device including an LC circuit, a first electrode coupled to one end side of the LC circuit, a second electrode coupled to another end side of the LC circuit, and a housing accommodating therein at least the LC circuit. The input support device is disposed overlapping with a plurality of the electrodes, the housing is a conductor, the LC circuit includes a first capacitor and a second capacitor coupled in series between the one end side and the other end side of the LC circuit, and a coupling portion between the first capacitor and the second capacitor is coupled to the housing.