Cross x Regalia

is a Japanese light novel/manga series written by Makoto Sanda who's also the author of Rental Magica, with illustrations by Yūgen, published by Kadokawa Shoten under their Kadokawa Sneaker Bunko label.

Plot
On the corner of Chinatown, the two of them crossed, The boy name is Inumi Haserou, high-school bodyguard who takes 1000 yen for each trouble; the girl name is Nata, self-styled Sage who mysteriously collapsed in the back alley. Deciding to protect Nata, Haserou would have to face the sudden change in his daily peaceful lives, as a group of Vampiric being who consumed people Ki, called [Demonic Sage] starts to attack them. Their purpose: to hunt Nata, who holds the key as the powerful weapons capable of turning them powerless!