There's swearing, gore, and even sex in these shows that you really would prefer an adult to watch them instead.
But once you dig deeper into these animated Japanese shows, you'll be surprised that it's definitely not made for anyone who isn't able to understand adult topics. And since not many people have gotten wind about the animated shows that came from Japan, they just dismiss it as something similar to Western cartoons where the target audience wouldn't be someone over the age of eighteen. While many people would argue that cartoons aren't made for adults, that won't exactly be the case when it comes to those that were produced in Japan.