When you think anime can't get dark and disturbing anymore, then you got Deadman Wonderland. Anime is about underage children going to a brutal prison.
Sekirei the best adult anime with a harem, romantic comedy, and supernatural elements.
The anime is far more disturbing, messed up, and believe me when I say it will make you feel disgusted. I personally think that it is one of the most hardcore r-rated anime out there.
Skeleton Knight in Another World
I have mixed feelings about this show, most people think it is a clone of the overlord, but it is not. But it is worth a try and yes I am going to continue this show,
In the year 2071, humanity is in danger of extinction following the appearance of man-eating monsters called "Aragami", it is one of the best r-rated action anime.
We know Highschool of the Dead is a popular r-rated anime tv show about zombies when suddenly in Japan dead began to rise and the city was in complete chaos.
There is no wonder that adult anime series are popular among audiences. This r-rated anime tv show is for mature adults