The protagonist you incarnate. Seeing school as a mere method to avoid stress, Kyousuke is an average high schooler, lazy with studies and hanging around with his friends, especially Eiichi. What he likes? Money but that's related to his lifestyle which isn't exactly as the appearances seem to be. The other true hobby he has a fond of is classical music, specifically Bach. Kyousuke shows little empathy and emotion throughout the story, only showing the slightest bit of either to manipulate others for his own benefit. This comes from his apprenticeship underneath Azai Gonzou ("The Beast"), who had "taught" Kyousuke that the only way to lead life was to be ruthless and care for no one but yourself, relying only on money and power to pave the way. As the story goes on, Kyousuke will be hit by the reality and will soon realize what he lost during all these years, with his bound with either girl, but that's not as easy as it sounds to be.
Haru Usami is the main heroine of G-Senjou no Maou. She has long black hair and is extremely intelligent with extensive skills in deductions. Haru has a long history with Maou but is hesitant to tell anyone about it. Ironically, she lacks prowess in martial-arts, something that Maou is aware of. It is later learned that Maou was responsible for the death of Haru's mother, which was explained by both Haru and Maou himself. The latter revealed that Haru's father was responsible for the imprisonment of Maou's and Kyousuke's father due to transfer of gambling debts through fraud (Samejima Toshikatsu killed Haru's father in a heat of revenge after learning about the debt). Despite this bad blood, Haru falls in love with the younger son, Kyousuke, later implementing his help to find Maou and bring him to justice. Ultimately, they succeed at the cost of Kyousuke being imprisoned for eight years for the murder of his own brother (when in fact he had taken the fall for Usami). Once released, Kyousuke learns that he sired a daughter with Usami, who had waited for him all that time.
Kyousuke's adoptive father, a fearsome and cruel yakuza boss called the Beast. He owns several corporations he uses to run his illegal operations, most prominently the Azai Group. He finances his daughter Kanon's figure skating career.
Haru's friend. Yuki is a very intriguing girl who seems to enjoy teasing people with her words and sharp understanding of behaviours and the like. Playful and mysterious, she likes Haru a lot, though the later is a bit reluctant and uneasy with her. Being the daughter of a Elite Police Investigator, Yuki learnt early human psychology and negociations basis, and soon, her outstanding skills became aknowledged among her father’s surrounding, but by Haru as well. Seiyuu: Hitomi (��美)
Rude is a tall, naturally bald man with a slight goatee. He always wears sunglasses and carries a number of spare pairs with him. Rude is rarely seen without his long-time partner, Reno, and is rather taciturn, tending to relegate the talking to Reno. Rude is a superb physical combatant and prefers to use his fists in battle. (Source: Wikipedia)