This anime always gave me a thrill, and personally, I absolutely love gore. It was a beautifully organized anime, but one thing I have to say:
Only watch the ending of you want your heart to sink to hell, be skinned alive, torn to shred slowly and painfully, and then burnt to an ashy crisp.
That is all I have to say about the ending.
Other than that, the art was well done, I have to say. Unless you don't like unnecessary gore, that is. It is very thrilling and will make you jump out of your seat every time the episode ends. It has fluffy moments, but other than that, it'll give you lots of feels. Like, as much as a whole bus full of elephants, along with a whale bus driver, making you give them a piggy-back ride. It does have the cliché main character, though, that is seeking revenge and such. His companion, Shiro, I'm sure you'll love sooner or later, and many creepy anime viewers were sure to have died of nosebleeds from Shiro during the series.
Other than that, I assure you'll love the 12 action-packed episodes, and hoping to dear God that there will be a sequel for the series.