Developing device and toner cartridge

A developing device to which a toner cartridge is to be attached, the developing device comprising:

• a developing roller comprising a rotational axis extending along a horizontal direction, the developing roller being capable of supporting a toner;
• a casing comprising a developing chamber for accommodating the toner to be supported by the developing roller, a feed opening for feeding the toner from the toner cartridge to the developing chamber, and a return opening for returning the toner from the developing chamber to the toner cartridge, wherein the developing chamber is defined by the developing roller;
• and
• a transporting member located within the developing chamber, wherein the transporting member transports the toner within the developing chamber from the feed opening to the return opening,
• wherein the feed opening and the return opening are offset along the horizontal direction, and
• the feed opening is located higher than the return opening, and
• the developing device is configured to accept the toner cartridge in a detachable manner.