An information processing system according to an embodiment includes at least one supplementary information processing apparatus and a main information processing apparatus. The main information processing apparatus is connected to each of the at least one supplementary information processing apparatus via a communication network. The supplementary information processing apparatus executes, on input information, arithmetic processing using a preceding network from an input layer to a boundary layer located at a predetermined position in a first neural network, and transmits intermediate information indicating an arithmetic result of the arithmetic processing using the preceding network, to the main information processing apparatus. The main information processing apparatus executes, on the intermediate information, arithmetic processing using a succeeding network from a layer subsequent to the boundary layer to an output layer in the first neural network.