Undead Murder Farce
A fantasy series with the world-building and stakes that define the genre.
In 19th-century France, the wife of vampire noble Jean Duchet Godard is murdered in her own home. With the local human authorities unwilling to properly investigate the case, Godard hires a pair of private detectives known to specialize in the supernatural: Tsugaru Shinuchi, a man with a mysterious birdcage; and his partner, Aya Rindou. This enigmatic duo has come from faraway Japan for one purpose—to track down the man who stole both Aya's body and Tsugaru's humanity.
Plot summary from MyAnimeList. Data and images via Jikan API.