1. An image processing device comprising: a Universal Serial Bus Interface (USB I/F) configured to receive USB data packets transmitted by a data processing device according to a USB protocol, and cause a specific buffer to store content data included in the received USB data packets, the specific buffer being a buffer corresponding to one USB endpoint for reception; and a control device configured to: execute one or more processing on the basis of a HyperText Transfer Protocol (HTTP) command; execute image processing on the basis of a particular command other than the HTTP command; and execute content data allocation processing, wherein the content data allocation processing includes: causing content data including the HTTP command stored in the specific buffer to be processed in the execution of the one or more processing; and causing content data including the particular command stored in the specific buffer to be processed in the execution of the image processing.