From Japanzai:

In the edges of this world, demons known as "Pagans" lurk. Pagans are born when the souls of the recently deceased fall off the path to reincarnation. The reincarnation ceremony must be performed under moonlight, and so cannot be performed inside a city like Faith-Dehli, overly shrouded by both constant mist and thick smoke.

The Twanbach Funeral Service Company specializes in hunting these Pagans, especially those that attack while Twanbach delivers recently deceased bodies to the reincarnation ceremony—because there's nothing Pagans desire more than freshly dead human bodies with the souls still slightly attached.

Reginald, a 100+-year-old vampire who looks like he's 20, gets scouted by the Twanbach Company owner's mysterious twin daughters, Vanessa and Veroinica Twanbach. But first, they'll hunt Reginald a little, to see how far off the path he's fallen...