I'm the translator. Uh, this manga is Akimi Yoshida's first serialization. It ran from 1978-1981, so obviously before Banana Fish. This manga is an actual shounen ai, it goes farther than even Banana Fish. I don't want to give much away, because it veers into spoiler territory. But any romantic tension you see between Heath and Eve is 100%, canonically there.
The short answer is kinda, the long answer is, I think the endings feel distinctly different, I can only hope that the tragedy doesn't keep you from reading more, lol. If you want full spoilers, you can dm here, or discord (My discord is the contact on the credits page). I'm so happy you like my translation btw, I really hope I'm doing this manga justice.
Is this manga related to banana fish?