An image forming system includes a toner container and an image forming apparatus to which the toner container is mountable. The toner container includes a projection that includes an inner peripheral surface centered on a central axis of the toner container. When the toner container is oriented in a predetermined direction, the projection has a downward guide surface facing downward and an upward guide surface facing upward. When the toner container is moved downward in a direction of the central axis toward a mounting portion of the image forming apparatus, (i) the downward guide surface is configured to guide a guided member of the image forming apparatus so that the guided member is rotated in a rotational direction about the central axis, and (ii) the upward guide surface is configured to guide the guided member so that the guided member is moved up after the guided member is rotated in the rotational direction by the downward guide surface.

A developer accommodating unit for accommodating a developer for image formation includes a flexible container provided with an opening 35a for permitting discharge of the developer, a frame for accommodating the flexible container and for accommodating the developer to be discharged from the flexible container, and an urging member 21 for urging a developer accommodating bag toward the frame for accommodating the developer accommodating bag 16. By this, it is possible to satisfactorily effect discharge of the developer from the flexible developer accommodating bag 16.

A toner container includes a storage portion configured to store toner and a communicating member including a receiving port, a discharge port, and a passage. The passage includes a first inclined surface and a second inclined surface connecting the first inclined surface and the discharge port to each other. When viewed in a third direction perpendicularly intersecting with both of a first direction and a second direction, the first inclined surface is inclined with respect to the second direction such that a more downstream portion of the first inclined surface in the first direction is closer to the discharge port in the second direction, and the second inclined surface is inclined with respect to the second direction such that a more downstream portion of the second inclined surface in the first direction is closer to the discharge port in the second direction.

An attachment for an image forming apparatus includes a projection having an inner peripheral surface centered on a central axis and projecting in a direction of the central axis outside the inner peripheral surface in a radial direction of an imaginary circle centered on the central axis.

There is used a toner accommodating container including: a bag-shaped accommodating portion having flexibility; and a toner accommodated in the accommodating portion, and including a silica particle. The toner has a value of Total Energy of 300 mJ or less in measurement of the Total Energy when a propeller type blade is caused to penetrate a surface of a powder layer of the toner manufacturing by applying a vertical load of 88 kPa in a measurement container in a powder flowability measurement device while the propeller type blade is being rotated at a peripheral speed of 100 mm/see of an outermost edge portion thereof.

A developer container includes a pouch, a communication member, and a cap. A marking including an arrowhead part and a parting line are formed on an outer peripheral surface of the cap. A rear end of the arrowhead part is disposed between a first position that is a position 45 upstream from a reference position in a direction of rotation and a second position that is a position 45 downstream in the direction of rotation. The rear end of the arrowhead part overlaps the parting line.

A developer accommodating unit for accommodating a developer for image formation includes a flexible container provided with an opening 35a for permitting discharge of the developer, a frame for accommodating the flexible container and for accommodating the developer to be discharged from the flexible container, and an urging member 21 for urging a developer accommodating bag toward the frame for accommodating the developer accommodating bag 16. By this, it is possible to satisfactorily effect discharge of the developer from the flexible developer accommodating bag 16.

A fixing portion 18c for suppressing movement of a developer bag 16 when the developer bag 16 is unsealed by moving a sealing member 19 is provided. By this, unsealing becomes easy.

A developer accommodating unit for accommodating a developer for image formation includes a flexible container provided with an opening 35a for permitting discharge of the developer, a frame for accommodating the flexible container and for accommodating the developer to be discharged from the flexible container, and an urging member 21 for urging a developer accommodating bag toward the frame for accommodating the developer accommodating bag 16. By this, it is possible to satisfactorily effect discharge of the developer from the flexible developer accommodating bag 16.

A fixing portion 18c for suppressing movement of a developer bag 16 when the developer bag 16 is unsealed by moving a sealing member 19 is provided. By this, unsealing becomes easy.