Earth was invaded by the Nefarious Monster Army thirteen years ago, but they were defeated in a year by the Dragon Keepers, who were humanity's great protectors! Since then, the monsters have been humiliated every Sunday in front of unsuspecting spectators. A single monster, D, wanted to change this, so he infiltrated the Ranger Force. D successfully acquired one of the divine artifacts with the help of the mysterious Ranger, Yumeko Suzukiri. These artifacts can permanently kill the monsters' immortal bodies. Unfortunately, D's encounter with the Dragon Keepers led to his unfortunate end. The question is, who will stop them now?