A developer storage container includes a container body and a shape forming member. The developer storage container is attached to and detached from any one of three or more mounting portions provided to an image forming apparatus forming an image using a developer. The container body has a side wall portion formed in a mounting direction to the image forming apparatus. The shape forming member is attached to the side wall portion in a mode to correspond to any one of three mounting portions, forming a first non-compatible shape corresponding to this mounting portion.