There's a difference between being cautious and being paranoid. This protagonist is so paranoid he would make those around him overly cautious to be near him.
Story: A world is terrorized by a Demon Lord, and so the beautiful Godess summons a hero (from Japan, obviously) to save it. Wow, how original.... The hero is very careful and paranoid, but still manages to deal with any problem that shows up when fighting the Generals of the Demon Army. Now let's follow his path to saving the world.
Honestly, I thought it was gonna be a good story with lots of humor. But the Hero is so paranoid
he needs to destroy the ashes from killed enemies. He needs to completely evaporate the moist in the air when killing slimes etc. It's so exaggerated it completely stagnates the story. But the worst thing of all is that there's no logical reason for him to be so overpowered. He stays in a room for a while and trains, and then he's suddenly leveled up a loooot. If feels really weak and rushed, like the author didn't even bother to create a training arc.
Art: The art is actually surprisingly good. The color pages are beautiful and the character designs are pretty nice. Even the black'n white illustrations are looking good. Unfortunately the story didn't share the same high quality.
Characters: *sigh* A Godess with huge tits, blond hair and an inflated ego, along with a paranoid and overly serious Hero. Frankly it's very hard to like these characters because they are so flawed, but that's probably the point. If feels like the author tried doing a KonoSuba, but failed spectacularly. So instead of being funny, it's awkward. The important Demons so far has been evil and sadistic, which is at least what you would expect.
Overall, I did not enjoy this novel series. And that's not because I hated the Hero. It's because the silly speed-leveling that happens way too early in the story. And unlike Kirito, this hero doesn't really do anything. He gets stronger prison style, training in a locked room, yet he becomes the strongest in the world in but a few days.
So with the art being the only slightly impressive thing about this story, I honestly can't see how they got an anime adaption...