Sometimes it's better just to stick with the trailer.

In the 1920s, Inaho revives the vampire Mosquiton alongside his servants the fire demon Honoo and the snow woman Yuki.
Inaho obsessed with the anaemic Mosquiton desires the O-Part, an artifact said to grant immortality so she can stay with the scrawny vampire forever, drawn to a mysterious pyramid in London, Inaho goes after the O-Part, what begins is a quest to discover the true meaning of the pyramids as well as the unwelcome return of Mosquiton's first bride Camille.
Yeah my disappointment is obvious that I really didn't like this anime, it's not totally unsalvageable as the TV series takes a different path but this OVA is just painful to watch.
Inaho is the most selfish brat in all of anime, not that we haven't seen this type of character before but no where is it explained why she loves Mosquiton nor have we seen any feature in her that makes anyone want to support her, I'm kind of glad that Camille shows up as a rival and that Honoo and Yuki aren't so willing to put up with her shit unless Mosquiton says so which considering he dies nearly every episode its impressive the two servants bother to stick around, I've completely lost control of the plot by the end and I'm actually happy Inaho never got her way.
The dub just made Inaho even worse due to no indoor voice as well as Mosquiton sounding way too goofy to be taken seriously as a vampire. It's a shame really, the trailer made this anime look way more interesting.
Final Verdict: Horrible protagonists become so annoying that the plot is lost in frustration, the TV series may save it but I'm not looking forward to it, especially if nothing changes with the tone.