Vassalord.

Charley, a cyborg vampire who does the Vatican's dirty work, is the thrall of the local vampire playboy Johnny Rayflo. As the two fight crime--and each other--hilarity, violence and sacrilege ensue! But can Charley resist his own desperate cravings for blood? Find out as the devilish duo go up aginst a childlike vampire princess, a mysterious branch of the Unitarian Church...and one another.

(Source: TOKYOPOP)

Note: Volume 2 includes the side-story "ZOUL HALF", published in Comic Blade Masamune summer 2003.