Kei × Yaku - Dangerous Buddy
AKA: Kei×Yaku: Abunai Aibou
Japanese Title: ケイ×ヤク －あぶない相棒－
Episodes: 10
Disc: 2
Audio: Japanese 
Subtitles: English / Excellent
Starring: Inukai Atsuhiro, Suzuki Nobuyuki, Hirata Mitsuru, Kuriyama Chiaki

Synopsis:
Three years ago, a disappearance known as the Joker case remained unsolved and the case was closed. Renewed interest in the case requires a second review of the evidence.

Investigator Kinoshita Ichiro from the Tokyo Metropolitan Police Department's Public Security Bureau is being asked to reconcile the investigation. However, he is given a very different mission. His assignment is to spy on a gang clan led by their young leader, Hanabusa Shiro. A mysterious man, Shiro has risen to become a wakagashira (young senior subordinate in the yakuza group) in three short years.