While the whole notion of medieval weaponry in a modern world seems pretty bollocks the manga in general is interesting. I wish we'd get chapters more frequently, but I'll gladly take what I can get.
The economy seems a bit strange. On the one hand, the economy seems to be in crisis enough that proper food is scarce and oil products very expensive. On the other hand, apparently a random newby adventurer is able to afford a decent car and driving around in it? That's not consistent if you ask me. The mood in the dungeon also seems way too light, not like people in a rough world about to enter a dungeon that might get them killed. The manga seems to be a bit unclear about how dire the situation is.
I'm just wondering why nobody else is visiting his new dungeon? I mean, the government knows about it so it should show up in some kind of database or at the very least have its existance spread around by word of mouth. MC even made a blog entry about it instead of trying to keep quiet. How things are there should be at least a few dozen people constantly scouring all information for new dungeons to be the first to loot them. It makes no sense that it is being ignored.