Mina Karnstein/Synopsis

Volume 1
Having finally moved in with Ryuusei's/Arthur's family, Mina decides to begin the first day as siblings by waking up the young man in the morning, doing so by straddling his lower body as a greeting. Calling it 'service on the first day of cohabitation', Mina's friendliness quickly turns to outrage as she pulls off the blanket covering Arthur, only to find several erotic magazines underneath. Seeing that they all had to do with little step-sisters, Mina accuses him of wanting to attempt lewd acts with them and begins to throw the magazines at Arthur. In the commotion, both teenagers lose their balance and fall out of the bed, further angering Mina when Arthur comes out on top. Coming downstairs for breakfast, Mina then finds Arthur being teased by Hinami and wonders if he's 'making a move' on her next, but being assured by Mikan/Le Fay that he's not that kind of person.

Before leaving for the day, Jin gets the group to take a photo together to commemorate their new family, promising to send the photo to the girls' mother overseas. Arthur then takes Mina out on his bike, asking her to guide him around town while they do some shopping. Taking the opportunity to ask him about the dream he was having that morning, Arthur vaguely describes it as probably being the result of a trauma he suffered as a child.

After completing their shopping, Arthur momentarily leaves Mina to unchain their bike. While he's gone, several thugs take the chance to move in on Mina, trying to convince her to go with them. Returning with the bike, Arthur asserts that she's with him, and unhesitatingly strikes one of the men with the front tyre of the bike, surprising Mina. Throwing an open container filled with pepper at them, Arthur then grabs Mina and rides away safely. Apologizing for causing trouble, Arthur assures Mina that it wasn't her fault.

Despite his reassurance, Mina remains upset over what had just happened. Suddenly declaring that they're taking a detour, Mina is then taken to an open park with a clear view of the city at sunset. Explaining that he'd heard about this famous spot before moving in, Arthur then promises to save Mina no matter what, as it's only natural for families to help each other out. Smiling, Mina tells Arthur that he's actually sounding like an older brother now. Before heading back home, Mina takes one last sad look at the scenery.

Later that night, after Jin leaves town for a business trip, Hinami and Mina agree to 'begin'. Arthur and Le Fay then re-enters the house after seeing their father off, and Mina remains awfully quiet while Hinami asks if Jin has finally left. Finally speaking up, Mina then requests for Arthur and Le Fay to leave the house immediately. Before either can respond, Hinami uses an invisible force to throw them against the wall, stunning the young siblings. Explaining that it was magic, Hinami transforms into her succubus form before revealing to Arthur and Le Fay that Mina is, in fact, the future Vampyre Lord. In shock, Arthur asks Mina if it was all true. Without any emotion, Mina coldly apologizes before saying goodbye as Hinami activates her memory spell.

Surprisingly, both Arthur and Le Fay are unaffected by Hinami's memory magic and quickly goes on the offensive, revealing themselves to be two of the 'heroes' who oppose the vampyres, demons and fallen angels. Summoning his weapons, the young man goes to attack Mina with Hinami jumping in between them. Before landing his attack, Arthur stops and tells them he and Le Fay doesn't care that they're vampyres or demons but asks them to leave due to deceiving them and their father. Without further conflict, Mina and Hinami leave the house.