The year is AD 2225. Kouji Aiba and Aoi Housen are trainee astronauts stationed at Liebe Delta, located on the edge of the Geduld Sea. During a routine dive procedure, saboteurs with unknown motives suddenly attack, causing the space station to plummet into the Geduld—a plasma field that connects all planets like a nervous system and destroys any ship that ventures too deep. With all the adults on board killed, the young astronauts must survive the long journey home amid growing tension among themselves. Meanwhile, the organizers of the sabotage watch and prepare to strike again.