Kurogane Taito is a freshman in Miyasaka High. After an injury that prevented him from practicing karate, which he excelled in since elementary school, he had always believed that he was an ordinary, regular guy. However, due to a forgotten promise exchanged with beautiful Vampire (Most Ancient Sorcerer) Saitohimea nine years ago, he was in fact no longer ordinary. Taito later went on to regain his memories after a certain incident, and was reunited with Saitohimea. Along with unlikely allies, Kurenai Gekkou, Miyasaka High's student council president and a genius bent on avenging his parents, and Andou Mirai, a cute lightning demon and familiar of Gekkou, they have to contend against Gekkou's twin brother, Kurenai Hinata, who sought to resurrect the powerful Vampire (Most Ancient Sorcerer) Bahlskra. Unknown to them, their destinies were already woven and foretold in an ancient prophecy of epic proportions.
- Taito Kurogane (鉄 大兎Kurogane Taito?)
- Voiced by: Shinnosuke Tachibana (立花慎之介Tachibana Shinnosuke?)
- A white/silver hair 16-year old freshman of Miyasaka High, the protagonist of the story, Kurogane Taito used to excel in karate when he was young, but later had to give it up due to a leg injury. Since then, he had believed himself to be an ordinary, regular guy. However, his memories of an event nine years ago were sealed up, during which he had made a contract with beautiful Saitohimea and acquired an extraordinary ability which grants him a conditional form of immortality. At the start of the story, he manages to regain those memories after a certain incident and goes on to reunite with Saitohimea. He later acquires further powers and swears to protect Saitohimea from the Tenma (天魔). While Tenma is normally translated as evil spirit or demon, in the story, it is a special existence different from the conventional evil spirit.
- Saitohimea (サイトヒメアSaitohimea?)
- Voiced by: Megumi Takamoto (高本めぐみTakamoto Megumi?)
- Excluding the sealed up Bahlskra, Saitohimea is the last of the Vampires. In the story, 'Vampire' is used as thefurigana reading of 'Most Ancient Sorcerer' (最古の魔術師). Saitohimea is described to have mischievous, crimson eyes, pink lips, and lavender colored hair which ends in a spectrum of colors. Since she was born, everyone around her has sought and hunted her for her powers, save for Taito, whom she fell in love with and subsequently formed a contract with. She later joins Miyasaka High as a student, and together with Taito, becomes part of Gekkou's student council and takes on the name of Himea Saito (沙糸 ヒメアSaito Himea?).
- Gekkou Kurenai (紅 月光Kurenai Gekkō?)
- Voiced by: Yuuichi Nakamura (中村悠一Nakamura Yuuichi?)
- Kurenai Gekkou, a freshman and also the student council president of Miyasaka High, is a self-proclaimed genius. Nine years ago before the starting timeline of the story, due to a certain deed committed by his younger twin brother, Hinata, Gekkou was prompted to constantly seek out power, initially driven by the fear for his life, and later motivated by the prospects of revenge. Gekkou is demonstrated to be quick-witted and highly intelligent. He wields an ancient fencing-like sword known as Spell Error, and is trained in several traditional arts of exorcism. As the student council president, he has made a contract with and is tasked to be guardian of the Holy Ground (聖地), a location with certain special properties over which Miyasaka High was built.
- Mirai Andou (安藤 美雷Andō Mirai?)
- Voiced by: Iori Nomizu (野水伊織Nomizu Iori?)
- Also a student of Miyasaka High despite her age, Mirai is a lightning demon that takes on the form of a cute, 14-year old bishōjo. Initially tasked to kill Gekkou, she later went on to form a contract with him. While she is considered to be an upper-class demon of noble blood, most of her powers are usually sealed away by Gekkou and can only be re-activated with his permission, upon which her hair will turn golden and her body will be wrapped in a vortex of lightning. She is described to be excessively boisterous and annoying to Gekkou, though on the flip side, she is often irritated by Gekkou's apparent indifference to her existence. Her favorite pastime is reading manga and drawing.
- Haruka Shigure (時雨 遥Shigure Haruka?)
- Voiced by: Mina (美名Mina?)
- A girl with medium length hair, Haruka is the classmate and childhood friend of Taito. She carries romantic feelings for Taito. Her role becomes more pronounced later in the story.
- Hinata Kurenai (紅 日向Kurenai Hinata?)
- Voiced by: Jun Fukuyama (福山 潤Fukuyama Jun?)
- Younger identical twin brother of Gekkou. Described to be cold and emotionless, he sees all other humans, including his own brother, as inferior to himself. He wields several powers, including the ability to summon different contracted demons and dimensional beings to do his bidding. Hinata wants to capture Saitohimea for a particular reason.
- Bahlskra (バールスクラBaarusukura?)
- Voiced by: Takehito Koyasu (子安 武人Koyasu Takehito?)
- A powerful sealed up Vampire (Most Ancient Sorcerer) at the start of the story. He has deep ties to Saitohimea.
- Izumi Aomi (碧水 泉Aomi Izumi?)
- Voiced by: Chika Horikawa (堀川 千華Horikawa Chika?)
- A delinquent of Miyasaka High. Due to a certain reason, she later became the secretary of Gekkou's student council.