Kazama Naoki is a crack detective at the private investigation firm Nemesis in Yokohama. He has a brilliant mind like Sherlock Holmes and solves every difficult case. But the true detective is actually his talented assistant Mikami Anna. The two of them, who make quite an odd duo, are searching for Anna's father Hajime. 

He is a scientist and went missing all of a sudden. Together with Kurita Kazuaki, the owner of Nemesis who is Hajime's good friend, Anna and Kazama seek clues to his disappearance. As they take on one puzzling trick-ridden case after another, they seem to find a hint related to her father each time that brings about a new riddle. Then they learn that the key to solving the mystery of his disappearance is a 20-year-old incident that has been buried in darkness. 

What Anna does not yet realize is that both Kazama and Kurita are connected to this incident