Material-D is a Material, part of the system Unbreakable Dark materialized as a clone of Hayate Yagami during the Dark Fragment Incident. Her name is first introduced in The Battle of Aces in English Material-D and in Japanese "Lord Ruler of Darkness" without specific ruby-kanas. The "D" in her name is believed to stand for "Darkness," which is associated with Hayate and the Book of Darkness. In The Gears of Destiny, it is revealed her rubied name is "Lord" Dearche, which may be shortened as Dearche. It is most likely a misspelling of "Lord" Dearche. She is properly spelled as "Lord Dearche" in Magical Girl Lyrical Nanoha INNOCENT (video game). Her device is Yersinia Kreuz. (Source: Nanoha Wikia)
Bleu is a member of the Gallia Knight Army, and brother to Damien, Jack and Janette. He is capable of leaping great distances and performing impressive acrobatic moves. Just like his older brother Jack, Bleu is a capable fighter and strong with a sword. He's seen taking down two royal guards with one swipe. Also he is a mage, he use his sword as an wand.
Y�ko is the female lead of the series. She has two main abilities. The first is jaen where she shoots a coiling strand of fire out of her fingertips. There is also dai-jaen which is just a larger, more powerful variation. The second ability is shukichi, an ability which allows her to teleport objects. Strangely enough, although she is generally fearless in the face of evil spirits, she is terrified of normal dogs. During an escape from Hake, she met the child Keita, who was with her for three days and shared his chocolate cake with her, which became one of her favorite things. Due to this incident, she wanted to become Keita's inukami to make a contract with him. Yoko has feelings for Keita and she gets angry whenever he flirts with other girls.
Keita is the male lead of the show. He was considered a failure by his family due to his attitude towards their ancient duty to vanquish evil, treating it like a parttime job, and his initial inability to find an Inukami to bond with. Even though Yôko becomes his inukami and is fully interested in him, he has a bad habit of flirting with other girls; it is later revealed that Keita is mortified by the thought that, if he should develop a relationship with Yôko, he might become the father of a litter of puppies, rather than of a human baby. He is frequently punished for his transgressions by Yôko, to whom he had to promise that he would be loyal to her, that he would be hers and that he would be her toy, to do with whatever she wanted, before she would contract with him. He wears a dog's collar as a symbol of this pact - an item he originally intended as his 'vow gift' to Yôko. Yôko has frequently landed him in jail by teleporting him into a public place without his clothes, causing him to be mistaken for a streaker and arrested for indecent exposure. Due to this, he has been named Ra-ou (Naked King) by the city's perverts (male and female alike). Keita possesses considerable athletic skills, can make frog-shaped talismans up to around the size of his fist from rubber which he can use to make ranged attacks and is a practitioner of xingyiquan. However, a shinigami named 'Sea of Violence' commented his martial arts skill lack style. Despite his many flaws, Keita has considerable redeeming qualities; he is determined, usually fearless and loyal to his friends and to people under his protection.