The Mamiya is a supply ship under the command of Yui Fujita.
The Mamiya carries food supplies for seafaring vessels of Yokosuka Girls' Marine High School. She's often seen with the repair ship Akashi, as well as her Kagero class destroyer escorts Hamakaze and Maikaze.
Due to its nature as a food supply ship, the Mamiya carries a small complement of cats on board. They prevent rodents from feeding on precious supplies, as well as the spread of the Totalitarian Disease.
Over the course of the events of Haifuri, the Mamiya and her support fleet were untouched by the Totalitarian Disease.
Under orders from Principal Mayuki Munetani, the support fleet was sent to rendezvous with the Harekaze. The fleet came under fire from an infected Tama manning one of the Harekaze's anti-aircraft guns. Fortunately, nobody was hurt and the ship suffered little damage.
During the Harekaze's mission to save the infected ships, the Mamiya kept the destroyer well-stocked with food for its crew.