Akuma-kun (ONA)

Occult agency schtick. Many come to mind. However, one of the least likely for people to recommend would actually be this. Uncannily similar plot too, just replace demons with vampires. 

Both Gegege no Kitarou and Akuma-Kun are adaptations of Shigeru Mizuki's works. Both have a goregeous art style that compliment the horror themes and tone. Despite Gegege 2018 being more kids oriented, with Akuma-Kun being much more gruesome and violent in tone, both have themes of death and human desires. 

Both Akuma-Kun and Hakaba Kitarou are adaptations of Shigeru Mizuki's work. However unlike their counterparts (Hakaba Kitarou being related to Gegege no Kitarou), these adaptations take a much darker approach to their respective franchises. They're gruesome and feature many depressing tales of death. They both also have a gorgeous art style that suit the overall tone. 

Both series have a tag-team pair taking on supernatural cases.