The Crow-boss is the main antagonist in the Cerberus manga-series, written by Takumi Fukui. He is the leader of a group of eight "Kuzure", malevolent animal spirits that were accidentally set free by Kei Tomitsuka, the main protagonist, who had then to become a "gravekeeper" to battle the fled Kuzure and imprison them again. His true name is never mentioned, with the other Kuzure referring to him only as "Crow-boss/master" or simply "Master". It is revealed that he discarded his actual name in an effort to avoid getting send to the graveyard, since the engraving of a Kuzure's name is an important part of the sealing ritual.
After first observing the gravekeeper from the shadows, he later took possession of the body of Fuyuko, Kei's teacher at school. When his presence was eventually revealed, he battled the boy, but was finally defeated and sealed away permanently.
As every Kuzure, the Crow-boss was originally a normal animal, living long ago in a feudalistic Japan. Not much of his backstory was shown, but what is known is that even back then he was a crow that was skilled at hunting, even ambushing a grown wolf by going for it's eyes.
When animals die after living a very long life, they turn into protectors of the world, called "pillars", but when the animal is filled with vengeful thoughts and desires, it's spirit refuses to become a pillar and instead lingers on, eventually turning into the shadowy being of a Kuzure.
Some time after becoming a Kuzure, the Crow-boss was hunted down by Tokoyo, an order of priests that battle evil spirits, and imprisoned in a special shrine along with seven other powerful Kuzure. He stayed there until Kei Tomitsuka released him unwittingly.
The Crow-boss's regular form is a dark seemingly partly liquid mass that is shaped like a huge monstrous crow. He has white eyes without a pupile and, even though crows are toothless, has many sharp teeth in his beak.
After he fully possessed Fuyuko's body, he appeared on her back in the form of a giant crow head and a pair of black wings, while also twisting her attire and forming her hands and feet into claws.
Even by Kuzure standards, the Crow-boss has a very cold and ruthless personality, treating even his fellow Kuzure like expendable tools or chesspieces used only to assess the powers and weaknesses of the gravekeeper. He also has a sadistic side, taking great pleasure in using Kei's emotions towards Fuyuko to torment and break him mentally.
The Crow-boss is a schemer who likes to hide in the shadows, making plots to defeat his foes while using others (the rest of the Kuzure) to fight his battles. He tries to avoid open confrontation and instead gloats over having everything under control from a safe distance. When he was eventually forced to fully manifest in Fuyuko's body and the school was encased in a very strong barrier by Tokoyo, leaving him no escape route and forcing him into a corner, he became quite desperate and cowardly.
The Crow-boss is first seen on the very first page of the manga, showing him among the other seven Kuzure sealed within the shrine in the old school building. After Kei accidentally released the evil spirits, they are shown amassing before the young boy, but the Crow-boss isnt visibly singled out from the others in that scene.
He is next seen in a thought of Yukifusa (the "cerberus" guard dog the manga is named after, who helps Kei by turning him into the battle-form of a gravekeeper) after the first three Kuzure have been defeated. Yukifusa mentions how the remaining five are probably much stronger and pictures them in his mind, with the Crow-boss clearly recognizable among them.
His actual appearance is a bit later, when he meets with a fellow Kuzure, Sannou the cat, in a narrow alley somewhere in the city. He is sitting on a heap of junk in a dead end of the alley, looking as if he is residing on a throne. Sannou is excited about the scent of the gravekeeper disappearing, wondering if he was killed, to which the Crow-boss responds that he should calm down, mentioning how the scent was lost because Kei is currently hidden inside some kind of barrier (he was in fact staying at a temple which serves as a gravekeeper training ground).
Some time later, the Crow-boss informs Sannou that he discovered the location of the gravekeeper.
When Sannou is eventually overwhelmed by the Gravekeeper and burned by the flames of Rikugo, he suddenly spots the Crow-boss sitting in a tree, watching the fight, but not coming to his aid. The cat then realizes he was set up so the crow could witness Kei's abilities firsthand. While Sannou curses his master with his last words, the evil bird simply flies away after smiling viciously.
School Excursion Arc
When the spider Kuzure, Gyouki, attacks Kei and his class on a field trip to old ruins in a park, he recalls the Crow-boss giving him a heads up about the gravekeepers location and wonders why the other Kuzure would do this.
Shortly after the defeat of Gyouki, the Crow-boss enters Kei´s school undetected by the gravekeeper and Yukifusa, since the evil crow spreads his presence through a distracting flock of crows amassing around the school.