Shinigami San

Kennin Gido is a detective. He belongs to a mysterious division at the Tokyo Metropolitan Police Department. He is the only member in the division. There, Kennin Gido reinvestigates cases that received not-guilty verdicts. He searches through testimony and evidence from those cases to catch the real criminals. Kennin Gido is called "Shinigami" ("Grim Reaper") by those around him.
(Source: AsianWiki)
~~ Adapted from the novel "Shinigami (Deka)" (死神刑事 (デカ)) by Okura Takahiro (大倉崇裕).