Free Collars Kingdom (フリーカラーズキングダム, Furī Karāzu Kingudamu) is a manga series written and illustrated by Fujima Takuya. The individual chapters were serialized in Magazine Z, and compiled into three tankōbon volumes released by Kodansha from February 2003 to March 2004.
Cyan is a young Abyssinian cat who lives with a boy named Kokoro and his parents in Ikebukuro. When Kokoro becomes sick, his parents abandon Cyan, leaving him in the basement of their apartment complex. Soon he discovers a group of stray cats called the "Free Collars", who control East Ikebukuro and believe that collars hold down cats' "Wild Spirit". Cyan is given the opportunity to join, provided that he removes his collar, the symbol that he is still Kokoro's pet. Cyan declines, opting to remain in the basement and await Kokoro's return. However, Cyan comes to realize that he must join the Free Collars if he hopes to survive and reunite with Kokoro. He removes his collar and joins them in their fight against Siam, a rival gang leader who wants control of East Ikebukuro and plans to rule the world and enslave humans.
In his ensuing adventures, Cyan grows close to the Free Collars, yet still longs for Kokoro. He becomes frustrated by Siam's continued advances on East Ikebukuro and his teammates' unwillingness to mount an offensive attack. Convinced that Siam must be destroyed, Cyan confronts her and learns she was once a Free Collar until her brother, Puriam, was chased onto a road by humans and killed by a bus. Cyan is able to defeat her, and, reminded of Puriam, Siam silently wishes him farewell. Soon after, Cyan learns that Kokoro had recovered but is moving away. Saddened by the thought of leaving the Free Collars, he meets Kokoro at the train station and gives him his torn collar as a memento. Kokoro promises to visit Cyan, and Cyan returns to his new friends.