Akatsuki no Ageha

Akatsuki no Ageha (朱月のアゲハ) is a manga written and illustrated by Kotori Kirihara.

Plot
Once again, the police are baffled by the serial killings of several young women. Kudou, a detective, is referred to a young girl by a friend. But this girl isn't what she seems - Kudou saw her at the crime scene. Apparently she's a vampire!!