I don’t know why the movie I referred to above was titled Black Rain. It was about Japanese counterfeiters. I think it had something to do with drug smuggling too. Not sure.
Here is the explanation for the film’s title:
“...Joyce helps him meet Sugai, who explains that making counterfeit US currency is his revenge for the “black rain”, or nuclear fallout, after the bombing of Hiroshima in World War II. ...”
https://en.wikipedia.org/wiki/Black_Rain_%281989_American_film%29#Plot