Bayron City -- a Mega-Float type city in the Pacific Ocean, which doesn't belong to any particular nation. As the mine for Orgonium, a new energy resource, this city is the most noticed in the world right now, and here special cases caused by demons called "D Hazards" has been occurring frequently. Only a handful of people know about the existence of D Hazards. They are handled by PMCs (Private Military Companies). Shu is a young man living in Bayron City who runs such a company, but his company is tiny. On top of that, he cherry-picks his jobs, so he is always in a bind for money. His life, both publicly and privately, is being supported by the beautiful high school girl Kisara who attends a school in Bayron City.

When Shinozaki started his new job, he didn’t expect his superior to be so…cute!? He struggled to learn the ropes until Katase, his tiny and kind senpai, took him under her wing. But as they grow closer, he hopes her attention might mean something more.

In the 21st century planet Earth was rendered inhospitable to life, and people mass-migrated to Planet Zi, the natural home of metallic life forms known as Zoids. Many years later, Zi faces its end. Its inhabitants partake the journey to migrate back to Earth. Attempting to regenerate the Earth to make it hospitable, the migrants come up with a "Zi-Forming" scheme. However, the plan fails and Earth is left in its state of turmoil. Overrun by Zoids and blanked by unstable weather phenomena, the migrants are faced with a difficult life. The Empire and Republic settlements attempt to uncover Zoids buried within the Earth to bolster their respective armies. The story picks up following second-generation Earth citizens: Leo Conrad and Buzz Cunningham, who have a chance encounter with a girl Sally Land as she flees the clutches of the Empire.