Earth Expansion Volume 1

It has been 50 years since a natural cataclysm unleashed a horde of monsters upon the Earth. In this new world, where effective human weapons do not exist, there are ''first-class pioneers'' who can transform themselves into strong warriors using the power of special crystals. Kuroki is a ''second-class pioneer'', who surveys the areas where the monsters have been wiped out. Along with his partner Pomukichi, a small dog, he sets out to investigate an area outside Tokyo. But when he gets there, a monster appears. Kuroki, a non-pioneer, has no countermeasures, until he accidentally discovers a crystal, and is transformed into a giant invincible dragon.