Vampires x Devils: Annihilation Master

I'm human, but I'm also a transmigrator. And a transmigrator always comes prepared. I have a Sacred Gear waiting to awaken, with a power that could shake the supernatural world, even if I'm not ready to wield it yet. My Vampire Princess is a badass—and she's about to turn me into one of her kind. I have a Gremory Heiress waiting to be found, a devil who could change my whole status. And an ambition that reaches from the Heavens to the Abyss. This world isn't ready for the new Dark Lord, Aono Tsukune. --- Disclaimer: This is a fanfiction crossover where various characters from other fandoms will appear thanks to the nature of the Annihilation Maker. The main worlds, Rosario + Vampire belongs to Akihisa Ikeda and High School DxD/Slash Dog belongs to Ichiei Ishibumi. I own only the original plot and my transmigrator's terrible decisions. — Description from novelcodex.org