An image forming system includes a first image forming apparatus and a second image forming apparatus. The first image forming apparatus includes a register and a first custom box. The register registers a share program for executing particular processing. The first custom box stores a job transmitted from the second image forming apparatus. The second image forming apparatus includes a communication device and a remote instructor. The communication device transmits the job to the first custom box of the first image forming apparatus. The remote instructor gives an instruction to the first image forming apparatus to start processing based on the share program. The first image forming apparatus includes a processing executor. Upon receipt of the instruction to start processing from the remote instructor, the processing executor executes the particular processing based on the share program on the job stored in the first custom box.