I recall fellow collaborator nikala writing about a Miyuki Nakajima（中島みゆき）song and remarking that the singer-songwriter's lyrics are often quite bittersweet (emphasis on the bitter) about romance and about the world at large. On reading this, I've started to notice that certain feeling with some of her songs and even the titles. And also with the song here.
"Abayo" (Farewell) was Naoko Ken's（研ナオコ）12th single from September 1976 which was written and composed by Nakajima, and I would probably say that it is downright bitter. The first two verses go as so:
There's nothing that says that guy is the world's best
As if nice guys were going out of style
For instance, over there in the neighbouring town
There are plenty of nice guys over there
So he's away today and tomorrow
What can you do if you're so hated
That he used such a transparent ruse
He's just putting on airs by saying farewell
Don't cry, don't cry, my love (for him)
That man, that man doesn't suit you
That sounds like a whole lot of "there's plenty of other fish in the sea" rationalization featuring a woman who's admonishing/reassuring herself in the mirror and not succeeding too well in the latter. She may be realizing that the marlin she just lost was perhaps the right guy for her after all.