Developer supply container and developer supplying system

A developer supply container detachably mountable to a developer receiving apparatus, said developer receiving apparatus including a developer receiving portion provided with a receiving port for receiving a developer and including a portion-to-be-engaged capable of displacing integrally with said developer receiving portion, said developer supply container comprising:

• a rotatable developer accommodating portion for accommodating the developer;
• a developer discharging portion which is rotatable relative to said developer accommodating portion and which is provided at a bottom side thereof with a discharge opening for discharging the developer accommodated in said developer accommodating portion;
• and
• an engaging portion provided only on one side of said developer discharging portion as seen in a direction in which said developer supply container is inserted into the developer receiving apparatus, said engaging portion is engageable with the portion-to-be-engaged with a mounting operation of said developer supply container to displace the developer receiving portion to move said developer receiving portion toward said discharge opening, thereby to bring the receiving port into fluid communication with said discharge opening.