In the year of 2046, the L.I.S.P. Space Station ends up getting attacked by enemy fleets. In response to this, the H.D.E. Leader sends three members of the Heroic Defenders of Earth on a mission to stop them. However, when the attackers are defeated, the H.D.E. defenders are thrown into a journey to figure out the secrets of Codename: STEP and save the alien world of Onerth!
