Another happy discovery on YouTube, this was the first ending theme for a TV Asahi Japanese cop program with a difference called "The Hangman"（ザ・ハングマン）which had a good long run from 1980~1987. It is interesting since anyone who wants to become a member of this elite force basically has to die...or at least give the impression that he/she passed away.
I've tried to read through the J-Wiki article on "The Hangman", and it seems to be a mix of a typically shibui Japanese cop show, the Arnold Schwarzenegger flick "Eraser", the 80s TV version of "The Equalizer" with the late Edward Woodward, and perhaps even "Charlie's Angels" (there is a recurring mystery man at the top of these hangmen). My assumption is that the members provide their own special brand of justice to criminals who would otherwise be out of reach of the usual long arm of the law. One line in the J-Wiki article has described the show as an updated version of the "Hissatsu"（必殺）series of jidaigeki shows which feature assassins with their own particular sets of skills.
Anyways, I first cottoned onto "The Hangman" when I discovered the ending theme for the first season of the show in 1980. Titled "A-re-ka-ra" (Since Then), it's sung by Osakan singer-songwriter Hirosuke（ヒロスケ）, or Hirosuke Fumita（文田博資）, who was most active in the 1980s. The nocturnal City Pop is overflowing here although I can pick up a sense of 1960s Henry Mancini jazz in there as well. My exposure to "The Hangman" has just been limited to the top video but perhaps there is a bit of classy style combined with the street grittiness in the show as a reflection of the song. The characters could hang out in a non-descript hole-in-a-wall while listening to "A-re-ka-ra". Mind you, when I hear it, I think about heading over to a Renoir cafe in Tokyo.