I do like it whenever an episode of "Uta Kon"（うたコン）yields a number of songs that I had never heard about. And it was a bounty of riches last night since the theme was Tokyo kayo.
Case in point: Shinichi Mori's（森進一）single from October 1977, "Tokyo Monogatari" (Tokyo Story). Mori will always be known as one of the top-notch enka singers but he has crossed borders, so to speak. In fact, the first song that I got to know him by was the definitely un-enka "Fuyu no Riviera"（冬のリヴィエラ）, a sweeping heroic-sounding ballad created by Takashi Matsumoto and the late Eiichi Ohtaki（松本隆・大滝詠一）.
Well, "Tokyo Monogatari" has somewhat of a film noir intensity about it, as in the old saying of there being a thousand stories in the city. With Tokyo, there are probably ten times that number. Like the later "Fuyu no Riviera", the song composed by Makoto Kawaguchi（川口真）also doesn't sound like enka but neither does it have that conventional Mood Kayo quality although I have categorized it as such. The J-Wiki article on "Tokyo Monogatari" ever refers to Mori taking on a Kawaguchi melody for the first time.
I have a number of Kawaguchi-penned songs on the blog but I never heard of the term "Kawaguchi melody". But taking a look at some of those tunes, I have the impression that the composer comes up with some hard-boiled music of the city, not so much taking place in the bars and nightclubs but out on the dirty streets of Tokyo. Perhaps there is a goodly amount of brassiness in the arrangement of his creations.
Lyricist Yu Aku（阿久悠）wrote the words about a typical story in the big life involving a high-class relationship in which at least one of the participants is not quite sure where it's going but is at least keeping a nonchalant face about it while perhaps harbouring a deep desire hidden away.
"Tokyo Monogatari" went as high as No. 20 and it earned Mori another appearance on the Kohaku Utagassen that year. As well, a 1977 TBS detective show "Ashita no Keiji"（明日の刑事...Tomorrow's Detectives）based its 4th episode on the song itself and even had the singer on in a guest role.