TV-Series
Description
Kō, also written as Kou, is a twenty-five-year-old member of the Rei, one of the two shadow races in the world of Monochrome Factor. He is a tall man standing approximately 184 centimeters and weighing around 70 kilograms, with black hair, purple eyes, and a small scar beneath his left eye. He typically wears glasses and a suit, and he is often seen smoking. Born on January 17, he has blood type B. Kō is a loyal follower of Ryuuko, the king of the Rei, who is the opposite of Shin, the race to which the protagonist Akira Nikaido belongs.

Kō first appears in the story as a perverted and mischievous individual, who often flirts with female characters such as Aya and Haruka, sometimes crossing boundaries. His introduction in the anime involves him lifting Aya's skirt, and he is occasionally depicted as a masochist for comedic effect. Despite this playful and seemingly carefree exterior, Kō hides a deep sense of guilt and carries a burden from his past. He is a cheerful and happy-go-lucky person on the surface, enjoying teasing others and maintaining a lighthearted attitude, but underneath he is troubled by his own actions and the consequences of his power.

Several years before the main story, Kō became friends with Akira Nikaido and Kengo Asamura after a mysterious event. This connection makes him a close ally and an older brother figure to the two, often being called Kouni by them. His scar was gained two years before the events of the series during a fight with Kengo, who had gone berserk after absorbing too much darkness. This incident marked a turning point in Kō's life and deepened his sense of responsibility.

Kō's role in the story is that of a supporting ally who aids Akira and his friends in their battles against the shadows. He is fiercely loyal to Ryuuko and serves the Rei king's cause, but his personal bonds with Akira and Kengo often place him in a position where he must balance his duty with his friendships. His perverted antics provide comic relief, but his serious side emerges in combat and whenever the safety of his friends is at stake.

As a member of the Rei, Kō has the ability to transform into a more powerful form, often referred to as his Rei or wolf form. In this state, he removes his glasses, as his eyes become cat-like, and he gains enhanced physical abilities. His body is covered with straps that serve to restrain and limit his immense power, and when he unleashes his full strength, his appearance has been compared to that of a vampire. In the manga, it is revealed that Kō is a factor of darkness, which grants him a high tolerance to the corrupting effects of the shadow world. However, this same nature becomes a danger, as absorbing too much darkness can cause him to lose control and go berserk, attacking anyone regardless of ally or foe. This volatile ability is both a strength and a source of internal conflict, driving his character development as he learns to control his power and confront his guilt.