K is a 2012 anime series animated by the studio GoHands and directed by Shingo Suzuki, who also serves as the character designer for the series.
A manga prequel called K: Memory of Red , drawn by Yui Kuroe has been serialized since May 28, 2012. Another prequel manga, K: Stray Dog Story also began running on November 2012.
Furthermore, two light novels, called K Side:Blue and K Side:Red , were released in October and November 2012.

Story:
A contemporary Japan ruled by the seven kings and their clans.
An ordinary high school student, Isana Yashiro, while tasked with helping out with the school festival, was suddenly attacked by men with red aura, accused for shooting one of the members of the Red Clan, HOMURA, and being targeted by its members for revenge. Driven into a desperate situation, Yashiro was saved by Yatogami, the Black Hound , a highly skilled swordsman on a mission to hunt down Yashiro on behalf of his late King and master, Ichigen Miwa. To prove his "innocence" and uncover the enshrouded mystery, he is accompanied by Neko and Yatogami.

The producers also green lit seson 2 of the anime.

Source:Wikipedia