Dungeons appeared on Earth. The kind you see in every template story. Suddenly, monsters emerged from these dungeons appearing all over, wielding inhuman powers and casting spells. Earth, now forced to coexist with these dungeons, gained access to new life forms, unknown technologies, and a power called "Skills," born from the magical pollution that accompanied the dungeons' arrival. So far, so good. Well, not really "good." In a template story, the profession of "adventurer" would be born, companies would buy monster materials and items found in treasure chests for exorbitant prices, and the world would enter an Age of Adventurers. That's how it goes in the templates, right?

...But it didn't happen that way. Reality is a cruel mistress. Think about it carefully. Companies buying massive amounts of monster materials? Come on, for samples, a hundred would be more than enough, wouldn't they? They wouldn't keep buying them indefinitely. So, the groundwork for adventurers was never laid. Naturally. Who would risk their life, even with skills, to delve into dungeons for no pay? Nobody, that's who.

So, what do you suppose happened then? Fortunately, Earth's weaponry *did* work against the monsters. They could be taken down with guns and missiles. Quite easily, in fact.

...But, they kept appearing every day. Probably because no one was delving into the dungeons to cull the monsters regularly. If only a few dungeons had appeared worldwide, things might have been manageable. But dungeons sprang up everywhere. From those with only weak monsters to others from which powerful ones emerged.

Every day, the military fought. They expended bullets like water and launched missiles with the extravagance of fireworks. You can guess what the result was, can't you? Faced with the disaster of dungeons—which yielded absolutely no profit—resources dwindled, and taxes skyrocketed... Eventually, all but the most crucial cities were abandoned. The situation became dire. Lawless zones sprang up everywhere, creating a world where even basic trade became difficult.

I live in such a future, decades later, in this world. For now, I plan to save the world with the skills I've honed for decades. Covertly, of course.

The method for saving it is simple. I just need to use my skill, "Equivalent Exchange Store." See? It's right there on that corner, like a vending machine. It seems you can exchange 10 F-rank monster cores for one basic potion.