It has been approximately 50 years since all monsters on Earth have gone extinct, marking the end of the monster era on Earth. Humanity had finally advanced to outer space, and a new era was formed called the Galaxy Crisis. The crews of Space Pendragon were tasked to investigate Planet Boris after communications on that planet mysteriously vanished. Arriving on the planet, the crew was astonished to find it inhabited by monsters, with every nearby city perished. While forced to wait for reinforcements, the crew must solve the mystery of this planet's background as a monster tamer named Rei, whose past remained mysterious, joined ZAP Spacy in order to learn his past.