At the Rice Mill, look for the small office building at the southern edge of the complex, outside the main mill. D8 is a reported search grid, not an exact door pin.
Enter the office and go upstairs. Look for the brown single door beside the pale-blue wall and confirm HOESIK SUPPLY ROOM on its unlock prompt.
How to get it
Unknown.
Observed room loot
A recorded opening shows a safe containing Infantry Invasion Plans; the player also reports weapons, materials and cash. Contents vary and no fixed key pickup is established.
