(that's actually Neuro in the background. Creepy isn't he?)

Majin Tantei Nougami Neuro ,Otherwise known as Demon Detective Neuro Nagami, is another murder solving mystery anime/manga. But this is no average CSI type story, for hell breaks loose (literally) in this anime.

Yako Katsuragi is a 16 year-old high schooler who has been forever plagued by the mystery surrounding her father's death. Found in his locked office with the blood of his corpse used to paint the walls (and alot of other disturbing details), the police have no choice but to rule Yako's father's death a suicide. After years of no evidence Yako meets, how should I put this, a demon by the name of Neuro. Neuro is a "detective" who has solved all the mysteries of Hell and has come to Earth in search of more. Neuro makes a promise to aid Yako in finding the secrets behind her father's death and in return he hopes to find the ultimate mystery to satisfy his hunger, literally. He feeds off of mystery and upon solving a case will transform into a horned bird and absorb the solved mystery from the murderer, often leaving the culprit in catatonic state of fear or confusion. Neuro is anything but a kind demon and refers to Yako as his slave, kicking her around. He is also very powerful, impervious to weapoms like guns (his excuse one time is actually that his blinking caught the bullet), and able to use the 777 tools of hells to assist him. Things really become interesting when reports of a mysterious murderer appear, who grinds his victims into gore and places them in a glass box. Yako believes that this "Phantom Thief Sai" may actually be responsible for her father's death. Every clue brings them even closer to Sai and closer to the horrible truth behind his twisted killings.

I'm going to recommend the manga for this series, mainly because it goes much farther into the story than the anime. But if you have the time, go through both. The manga is pretty well drawn and the anime is well animated. The only real thing to keepin mind is that the murders in this anime/manga are very unlikely to have worked and the motives are strange to say the least, but still, it' s an anime. And on final side note, it's gorey and at times disturbing (think tons of blood and lots of screaming) but that's just a small problem in an interesting series.