Note: The joke in this anime is that the protagonist is mentally challenged. That's the joke you're supposed to laugh at. Of course it's not outright said, but one look through other reviews (and watching the first couple of episodes) makes this pretty clear.
This is another fantasy anime about someone who has one really great skill and is overlooked because of stuff. Sorry, I simply don't have the energy to explain this premise again. If you're new to it, look to another example before watching this. Our protagonist is dreadful, that much is bad enough. Worse than that though is everyone around him, who simply goes along with it for mysterious reasons. He meets the king, is incredibly rude and gets given the most amazing sword because, well, it's funny?! The joke there is that he doesn't know it's the king, btw. In fact, it appears to be that he doesn't know what a king is.
Don't waste your time, if you're in the mood for this then Ossan Newbie is also on this season. It's not great but it's at least an outright comedy.