Developer container and image forming system for accommodating powder or liquid contents

A developer container configured to accommodate a developer, comprising:

• a pouch including an opening;
• a communication member configured to make inside of the pouch communicate with outside, the communication member being fixed to the opening of the pouch;
• and
• a cap configured to be detached from the communication member by rotation with respect to the communication member, the cap including a marking indicating a direction of rotation to detach the cap from the communication member, the marking including an arrowhead part formed to protrude from an outer peripheral surface of the cap, the outer peripheral surface being configured in a cylindrical shape, the arrowhead part including a rear side end portion located upstream and a front side end portion located downstream in the direction of rotation,
• wherein a direction connecting the communication member and the pouch is a first direction, a longitudinal direction of a cross-sectional shape of the pouch is a second direction, the second direction being orthogonal to the first direction, and a direction orthogonal to the first direction and the second direction is a third direction,
• wherein in a state of the cap attached to the communication member, the cap has a reference position on the outer peripheral surface, the reference position being a position in the second direction corresponding to where a thickness of the pouch in the third direction is maximized in a case where the pouch is viewed along the first direction, and
• wherein a rear end of the rear side end portion is disposed along the outer peripheral surface at an angular position within a range from 45° upstream to 45° downstream from the reference position in the direction of rotation, with the rotation axis as a center of rotation,
• wherein the front side end portion of the arrowhead part is formed such that a width in the first direction becomes narrower toward the downstream in the rotational direction, the marking further including a shaft part formed to protrude from the outer peripheral surface, the shaft part being continuous with the rear end of the rear side end portion of the arrowhead part and extending in the direction of rotation, the shaft part having a width narrower in the first direction than the rear side end portion.