The Weapon Of Raid Machines (WORMs), which devastated the Earth have been sighted once again. Three young girls are gathered at the Oppama base, and trained to pilot Sonic Divers. They learn they have been chosen to save the Earth from destruction. Aboard the secret vessel number 113, the Koryu, Sonic Diver Unit team members Eika, Otoha, and Karen help protect Earth against the WORM threat with their flying exoskeletons (in the TV series, a fourth then fifth girl is later added).