USB Host - Host (PC) from Android
The link topology on your diagram contradicts USB topology. The hub is a host, and PC is a host, and USB does not allow direct host-host communication. 

What you might need is so-called "USB Transfer Cable", like this Belkin Model F5U279. It has some sort of USB&lt;->USB bridge, I am not sure what is inside. They claim it operates at HS (480 Mbps) rate, and they are designed for file transfers. However, the link works (has drivers) usually between two identical Windows OS, so I am not sure if Android supports these devices.

Technically there should be PCI/PCIe add-on cards that could go into PC slots and present themselves as USB devices, but for some reason they don't exist, except one very special card that is used in USB-IF certification as a special reference USB device. [ As Tom Carpenter commented, there is USB3380 pripheral controller designed by Broadcom/Avago/PLX, but... "Software development is required. To obtain RDK, please contact PLX Sales Representative or Distributor", which might be challenging]

ADDITION: The "USB Transfer cables" are usually based on Prolific PL-25A1 bridge chip, which essentially is made of two USB devices with FIFO buffer in between supporting bulk transfers.