The story begins in 12th century Japan, and focuses on a character named Kuro; he is loosely based on a legendary Japanese swordsman named Minamoto no Yoshitsune. Kuro and his servant, Benkei are on the run from Kuro's older brother; Kuro's brother wants to take Kuro's life. While they're on the run, they find a house and they go to seek shelter.
In the house, Kuro and Benkei meet a beautiful woman named Kuromitsu. As the pair talk with her, Kuro shows signs of pain. Kuromitsu determines that Kuro is running a high fever, and she lets the pair stay; however, they must not look in the back room, regardless of what happens. Benkei agrees to this condition.
The next day, Benkei leaves to get medicine for Kuro. While Benkei is gone, Kuro spends time with Kuromitsu and falls in love with her. That night, Kuro's pursuers find Kuro at the house. While fighting with the pursuers, Kuro discovers that Kuromitsu is actually a vampiric immortal. The first episode ends with Kuromitsu offering Kuro eternal life.
I have to admit that when I watched the first episode of Kurozuka, I thought that it was rather slow to get going. The first several minutes focus on Kuro battling some of his pursuers, and there's little to no dialogue during this sequence. Even after Benkei enters the picture and finishes off the first battle, the story doesn't truly get going until the pair arrive at Kuromitsu's house.
Probably one of the most notable things about Kurozuka is how much blood is spilled during the battles. Considering that Kuro is loosely based on a legendary swordsman, this probably shouldn't be too surprising. There is also a scene with Kuro and Kuromitsu where Kuro is so filled with lust for Kuromitsu that he nearly forces himself on her.
The Crackle service gives Kurozuka a rating of TV-14. Between all the blood in the first episode, as well as the scene with Kuro and Kuromitsu in that episode, I would personally recommend Kurozuka for anime viewers who are 16 or 17 years of age and older.