In AD 2225, Kouji Aiba and Aoi Housen are astronauts in training aboard the space station Liebe Delta, positioned at the edge of the Geduld Sea. During a routine dive, unknown saboteurs strike, causing the station to plunge into the Geduld, a vast plasma field that connects all the planets like a nervous system and crushes any ship that strays too far. With all the adults on board killed, the young crew must survive a long journey home while tensions rise among themselves. Meanwhile, the saboteurs observe from afar and prepare for a second assault.