An information processing system includes a storage device configured to store therein information of a trained model, and a processor. The processor performs a detection process based on the information of the trained model, and outputs position information detected in the detection process, the detection process being a process that detects the position information about an object from a detection image. The trained model is trained based on training data in which an object in a training image is added with multiple annotations, and is trained to output position information about the object in the training image based on an overlapping relationship of the multiple annotations.