Barbarian in Tokyo

Kano Fubuki simply looked too young for his age. That was all well and good, but people found it hard believe that he was a bonafide detective, especially Kagetsuna Daimon, the head of a yakuza group involved in a current investigation. But when Fubuki is kidnapped, he's about to find out that Daimon has more of a personal attachment to him than the criminals.