Akatsuki Kain is a character from the second season of the anime Vampire Knight Guilty. He is a noble vampire and a student in the Night Class at Cross Academy, where he serves as one of the close confidants and right-hand men to the powerful pureblood Kaname Kuran. Known for his calm and collected demeanor, Kain stands out among his peers not only for his personality but also for his physical appearance. He has a tall, muscular build, tanned skin that contrasts with the typically pale complexion of many vampires, burnt-orange eyes, and short, brownish-orange hair. He is often seen with his uniform shirt unbuttoned, which has earned him the ironic nickname "Wild" from the human Day Class girls, as his behavior is actually quite mellow.

Kain was born into a noble family that is part of a pro-monarchy faction often associated with the Aido and Souen clans. He is the cousin of both Hanabusa Aido and Ruka Souen, having grown up closely with them from early childhood. His initial reason for attending Cross Academy was largely to watch over and protect his two cousins. As a person, Kain is defined by his perceptiveness, patience, and unwavering loyalty. He rarely loses his temper and frequently acts as a mediator, often needing to rein in the impulsive and heated arguments between Aido and Ruka. Despite not being directly responsible for their actions, his association with his more outspoken cousins often draws him into trouble, and he is a character who is frequently a victim of circumstance. His loyalty is deep-seated; he is the type of person who would never betray his friends, and he follows Kaname primarily because Ruka does, though he holds a personal hope that he will one day be able to believe in his own path.

Within the story of Vampire Knight Guilty, Kain's primary role is as a supporting figure and a protector. He acts as a messenger for Kaname and remains one of his trusted operatives as the conflict between vampires and hunters intensifies. His sharp perceptiveness comes into play early on when he is among the first to suspect Zero Kiryu in the death of the pureblood Shizuka Hio, a fact he dutifully reports to Kaname. Throughout the series, he remains a constant, stabilizing presence, often seen leaning against a wall with his arms crossed, quietly observing the events unfolding around him. In one notable instance, he is tasked by his cousin Hanabusa to search through records at the Aido family villa for information on anyone who might hold a grudge against the Kuran family, demonstrating his willingness to perform diligent, behind-the-scenes work for the sake of his group.

The most significant driving force behind Kain's motivations and actions is his deep, unrequited love for his cousin, Ruka Souen. His entire loyalty to Kaname is conditional and secondary to his devotion to Ruka; he follows the pureblood not out of personal conviction, but because Ruka is hopelessly in love with Kaname. Kain is acutely aware of this painful dynamic, once remarking that even when two people know their loved ones will never look their way, they cannot erase the small hope within them that continues to hope in vain. He has explicitly warned Kaname that if he ever causes Ruka unhappiness, he will never forgive him. This protective instinct reaches its climax during a critical battle when Kaname, wielding an anti-vampire weapon, severely injures Ruka. Seeing this, the stoic Kain is finally driven to rage, hurling a fireball at Kaname and declaring that he will never forgive him. In a pivotal moment that follows, Yuki Cross offers her blood to heal Ruka, but it is Kain who acts, drinking the blood from Yuki's wrist and then transferring it to Ruka through a kiss, an act that finally and publicly reveals the true depth and nature of his feelings for her.

In terms of development, Kain's character arc is one of quiet endurance leading to a decisive, self-affirming action. For much of the series, he suppresses his own desires, content to follow Ruka and ensure her safety from the shadows. His defining moment of defiance against Kaname, for whom he has great respect, marks a significant shift, proving that his love for Ruka is the singular principle that can override all other allegiances. By the end of the narrative, it is shown that his devotion is ultimately reciprocated, and he and Ruka end up together.

As a vampire aristocrat, Kain possesses the standard abilities of his kind, including accelerated healing, enhanced strength, speed, and acute senses. He also has the ability to alter or erase the memories of humans, a power commonly used by the Night Class to protect their secret. What makes him uniquely formidable is his specific magical ability to generate, manipulate, and control fire, an elemental power he can use as a weapon, as demonstrated when he conjures a fireball to strike Kaname.