In Shizume city there's a legend about a red king with demon-like abilities that single-handendly created the Homra organization, as long as you get accepted into Homra, you can gain extraordinary powers.
A novel adaptation of K, focused on the history of the blue clan and the events which led to Munakata Reisi's appointment as the current blue king.
Yatogami Kuroh has lost the only thing remotely close to family he had left—and to make matters worse, he's been charged with a final task by his master that he isn't entirely sure he'll be able to fulfill. Follow this young modern-era samurai as he sets off on a quest to track down the next Colorless King and determine if he's evil or not…and to strike him down where he stands if he is.
Novel adaptation of K, tells the story of how the current red clan was created, the background story of Kushina Anna, and details of Kamamoto Rikio, Yata Misaki and Fushimi Saruhiko joining the red clan and their time together as a clan.
Novel adaptation of K. This is focused on Isana Yashiro, Yatogami Kuroh, and Neko.
Tokyo Regional Legal Affairs Bureau Census Division, Annex 4 also known as SCEPTER 4 is a police institution that aims to stop criminals with special skills. But for them, their real target are... ?
The story takes place in a world where seven people with unusual powers are crowned as “kings,” and revolves around the “bonds” and “fate” between the people involved. (Source: Anime News Network)
Shiro and Kuroh are not the only ones who go to high school. Instead, the members of Homra (including their leader Suoh) and the members of Scepter 4 attend school together. The students are sometimes lax, but at other times, they are hot-headed.
Focused on Yata's and Fushimi's past. There are three parts: "Meeting," "Getting Along," and "Betraying."
In the *K* novel series: V.1 - *Side: Blue* - Focuses on the history of the blue clan and the events which led to Munakata Reisi's appointment as the current blue king. (Takes place before the anime, but after the events of K Side: Red) V.2 - *Side: Red* - HOMRA in its early days and Anna's initiation to the clan. V.3 - *Side: Black & White* - The silver clan between episodes 7 and 8 of season 1, focusing on flashbacks to Kurou, Neko, and Shiro/Weissman’s past. V.4 - *R: B* - Suou Mikoto, leader of HOMRA, was strengthening his clan in Shizume Town. Munakata Reisi, the Blue King just enthroned, immediately reorganizes Scepter 4 and re-establishes order. When these two polar opposites meet, conflict is inevitable! V.5 - *Side: Green* - Features Gojou Sukuna as the main character, and follows his rise through the ranks of JUNGLE.

