In AD 2045, a group of military cadets attending the preparatory course at the Central Military Academy traveled to the space station Aries for training. This group included Ryota Aizawa and his classmates, such as Sayaka Nagase and Kazuhiko Nitta. The situation deteriorated when a terrorist organization known as "Jararacas" seized control of the station. Although the military managed to evacuate the station, Ryota and his group remained trapped aboard. To make matters worse, the boarding assault resulted in the deaths of most military personnel, effectively leaving the cadets on their own. An unexpected twist unfolds when a mysterious virus is released within the station, taking control of nearly all personnel and transforming them into mindless creatures. This development forces everyone, both allies and enemies, to find a way to escape the station alive.