In a container is adapted to be coupled with another container, a first wall member defines a first storage space adapted to store developing agent for forming an image on a recording medium. A first coupler is adapted to be coupled with a second coupler provided with the first another container. A first communicator is operable to communicate the first storage space with a second storage space provided with the first another container by way of the first coupler and the second coupler, when the container is coupled with another container.