In the dark and terrifying underworld, there is a mysterious organization called "Ten Kings Hall" which is equivalent to the police station. In addition to judging some sinful dead, the Ten Kings Hall also undertakes the important responsibility of investigating abnormal deaths in the world. The cheerful and peaceful young man Mato Tsuzuki (voiced by Shinichiro Miki) works here. With rich experience in handling cases, he gradually becomes the backbone of the Ten Kings Hall. A series of mysterious murders occurred in Nagasaki, suspected to be the work of cruel and bloodthirsty vampires. In order to investigate the truth of the incident, Mato Tsuzuki and his partner Mitsu Kurosaki (voiced by Mayumi Asano) began their dangerous journey. With the help of his friends Watari On (voiced by Junyan Guan) and Shinichiro Tatsumi (voiced by Tomoyuki Morikawa), all clues point to a perverted doctor named Kazuki Iku (voiced by Sho Hayami). What Mi didn't expect was that in the past, Kazuki Iku and Mato Tsuzuki actually had an unclear entanglement, and Mato's past, which had been buried for a long time, gradually surfaced.