A dungeon has appeared on the earth. It’s a dungeon, like what everyone knows, a template dungeon. Suddenly, monsters appear in the dungeons that appear in various places, using a power that humans had never seen, like casting magic. The Earth, which has come to coexist with such dungeons, has been filled with unknown lifeforms, unknown technology, and skills created by the mana pollution caused by the appearance of dungeons. That’s good. No, it’s not good. The profession of adventurer was born, and each company bought the materials of demons that can be obtained and the items that can be obtained from the treasure chest for a large amount of money, and the world became an era of adventurers… That’s the templates, right? …Well, it didn’t happen. The reality is harsh, more than you think. Think carefully. The companies will buy large quantities of monster materials? Sure. But if it’s just a sample for research, 100 bodies are more than enough, right? Yeah, that’s right. They didn’t keep buying. Therefore, there was no basis for an adventurer to be born. Of course, that means, anyone dives into the dungeon for no reward. Even if they have the skills, are they willing to risk their life? Of course, no. Then, what do you think will happen? Fortunately, the weapons of the earth worked on the monsters. So, people were able to defeat them with a gun or missile. It’s that easy. …But they appear every day. I’m sure it’s because they don’t dive into the dungeon and thin out monsters on a regular basis. Well, if only a few dungeons appeared in the world, it was still good. But dungeons were everywhere. From dungeons with only weak monsters to dungeons with strong monsters. The army fought with them every day. Using ammunition like hot water and shooting missiles like fireworks. Do you know what the result will be? I’m sure you know. In a situation where the dungeon is not profitable at all, it becomes a disaster, resources will go low and taxes will go high… Eventually, people abandoned all but the important cities. That sound like a disastrous situation, right? Well, in such a world, lawless zones are everywhere. And even if you want to do some trading, it’s not easy. In such a world decades after that incident, I am still alive. And for the time being, I plan to save the world with the skill I have trained for decades. Secretly. It’s easy to save the world. I just need to use my skill “Equivalent Exchange Store”. You see, it’s in the corner, something like a vending machine. Hear me, it seems that 10 F-rank monster cores can be exchanged for 1 low-rank potion.