18+ Detective File 1: Kindan no Ai

Private detective Takayasu Higishino rescues Ayane from two men who cornered her in an alley. Ayane is startled by Takayasu's appearance, he looks just like her presumedly dead brother Shingo. Shingo's car accident occured under strange circumstances, and Ayane has hired Takayasu to help her find out what really happened. Takayasu suspects Ayane's family maybe involved, so he heads back with Ayane to her family mansion, posing as Shingo, hoping to uncover the truth.

(Source: ANN)