1. A simulating system comprising: a data retrieving device that time-sequentially retrieves a control value, which is outputted from a control system in an image forming apparatus to a controlled system, and an input value, which is inputted from the controlled system to the control system as a simulated control result of the image forming apparatus, the simulated control result being a control result that would be generated by the image forming apparatus if the image forming apparatus had executed an operation based on the control value; a data storing device that stores a time-series data group including a plurality of the control values, which have time-sequentially been retrieved by the data retrieving device, and the input values corresponding to the control values; and a simulating device in the controlled system which simulates the operation based on one of the control values and which generates the simulated control result corresponding to the one of the control values as a result of the simulating of the operation, wherein a correlation between each of the control values and the input value corresponding to each of the control values included in the time-series data group stored in the data storing device is implemented by the simulating device, wherein the control system controls operation of the image forming apparatus when not interacting with the controlled system, and wherein the controlled system virtually constructs the image forming apparatus.