She is the ruler of the Tepes clan of vampires; she is considered Queen of all vampires. Despite her appearance, she is much older than twelve. She is a hard and proud ruler intent on preserving the race of vampires.
Mina is the daughter of the former vampire queen Lucretia Tepes. When Mina was still young, her mother was murdered during the vampire clan war. She has been head of the Tepes family ever since. The Tepes are one of four noble, pure-blood vampire families. Mina has successfully made it the most powerful of the clans, thus she has established herself as queen of all vampires. She has many people vying for her life and power, notably the heads of the other three vampire clans. After living for a long time in secrecy, she finally reveals herself and subsequently, the existence of all vampires to the world. She purchases an island close to Japan, called Tokyo Landfill #0; it is at the same time, a colony of Japan and an independent nation. The island is where Mina plans to establish her new kingdom--a "bund"; only vampires live on the island, and none are allowed to leave (there are exceptions though, like Mina herself). She pays off Japan's national debt thereby and imports a large number of successful and vampire owned businesses into Japan in order to help boost the economy. She thereby forces the nation to concede the island and submit to her demands by not intervening in vampire affairs.
Mina is a ruthless leader, seemingly cold and harsh. She is strong willed, refusing to back down even when her life is at stake. She will not hesitate to resort to blackmail, violence, extortion or any other illicit tactics to ensure the safety of the bund and the preservation of the vampire species. She is skilled at not expressing any thoughts or emotions on her face. She accepts the advice of only a few trusted people, but she more often than not, remains sole control of a situation.
She does have a softer side though which is often shown around her personal guardian and lover Akira Kaburagi. When together, she acts more playful and youthful -- like an actual twelve year old girl. However, she is prone to become jealous and petty about Akira. She is very mean towards Yuki, another a girl in love with Akira. She is prone to testing his loyalty and love. Several times, she has purposefully put herself in a precarious situation, telling him the choice is his whether to save her or leave. On one occasion, she forces him to fight her in her true form. Nevertheless, She is very protective of Akira; she becomes enraged when his life is threatened. She sometimes will push him away and refuse to explain things to him, in order to keep him safe or allow him some peace of mind.