After a disaster at the Liebe Delta training station, 487 young people escape aboard the mysterious spacecraft Ryvius. With the adults gone, they wait for rescue. Attacks keep following the ship, forcing a stranded student population to fight for survival.
A vessel can provide shelter without providing a functioning community. The premise leaves the young survivors responsible for living together as well as keeping the ship alive, while outside attacks prevent an easy wait for help. Their training environment has become the entire practical world available to them.
During the evacuation, the elite navigation students called Zwei attempt to get people out aboard a training ship. Specialised education suddenly carries practical authority. The crisis begins sorting pupils by what they can do and what others need from them, before a stranded population has time to agree how it should be governed.