Gainer Sanga, who lives in Domepolis Urgusk in Siberia, is a high school student who loves games. One day, Gainer, who was suddenly imprisoned on suspicion of being an unknown Exodus, met Gain Bijou, who was also imprisoned, and escaped together. Gein was an Exodus contractor who was tasked with escaping the inhabitants of this Domepolis. Gainer activates the old overman that was kept at the mansion of Prince Medaille, who governs Urugusk, and lets Gainer operate it, and takes away Princess Anna, the daughter of Prince Medaille, as a hostage until the success of Exodus. Gainer fights against the silhouette machine of the Siberian Railway Guard that raids with an overman named King Gainer. He unwittingly helps Exodus.