In the near future, mutant creatures called Ruffians ravage Japan, and the Armed Volunteers meant to curb the threat oppress her people. Killed by Ruffians, Saki Amamiya was resurrected by the mysterious Achi, gaining superhuman abilities. Joining Savior Group, Saki fights for Japan wielding the Dolphin, a beam-powered gunsword. However, Achi hides grander plans for Saki, and the fate of the world may just hang in the balance!