Mercenaries are privately-operated military groups for hire. This page describes covers the status of mercenaries in the SARPiverse.
In the Yamatai Star Empire, private military forces have been banned since the Military Centralization Act of YE 28. Private security forces are still legal so most groups of this type brand themselves as security contractors.
Takeda Fleet provides fleet management services, primarily to internal Yugumo Corporation clients, and are not mercenaries per se, but their mission often includes security, escort, investigation, intelligence, reconnaissance, and other paramilitary services. They are employed when visual distance from the Star Army of Yamatai and other official Yamatai Star Empire ships and personnel is necessary for discretion. Thank them when your Kikyo Pie arrives without the delivery-person getting vaporized.