Yako Katsuragi is a high school girl whose father has just been murdered in a very strange way. She soon meets a mysterious individual called Neuro Nougami, who is in fact a demon from the underworld. It turns out that Neuro eats riddles and mysteries and having consumed all that the underworld has to offer he has come to the real world to search out more.
Neuro offers to help Yako solve the mystery of her father's death if she agrees to help him seek out more cases to investigate. As such Yako becomes the head of a detective agency and begins to help Neuro solve strange and confusing mysteries.
Neuro - Supernatural Detective
"DIRTY" by Nightmare
"Kodoku no Hikari" by Kagami Seira