Einhänder takes place in a future where a war between Earth's colony Sodom and the Moon colony Selene already has one catastrophic conflict behind it. The First Moon War left most of Earth's surface in ruins and installed a totalitarian regime on the planet. Now the Second Moon War begins: Selene attacks Earth again for natural resources, using single-pilot spacecraft called Einhänder—deployed on kamikaze runs designed to cause maximum damage before destruction.
Players take the role of one of these pilots, guided through their missions by the military satellite Hyperion and an on-board computer called EOS, which records every engagement and relays the data back to command. When the final objective is complete, Hyperion delivers an unexpected reward: the pilot's combat data has been used to perfect the latest EOS unmanned fighter. As recognition of their service, they are selected as the final test target for that same machine.
Surviving what follows raises a question the pilot can no longer ignore—why they were ordered to die by their own side, and what the war was actually being fought for.