Smoky Nectar

Mitsuru Hasegawa is a reporter looking into an incident suspected to involve a vampire. Yusei Annaka, or Anna, a friend he's known since they were kids, warns him not to stick his nose in too deep. He should know―he's a vampire himself. Mitsuru agrees to let Anna suck his blood as part of his research, and one thing leads to an incredible experience. Mitsuru's about to learn a secret about himself he had never imagined...!
(Source: Renta!)
Note: Includes an extra chapter.