>>53291709>to some irrelevant western moviethe absolute STATE of Luis
The Great Gatsby is a very famous book and read by most people in high school (which you probably didn't graduate from). Not to mention two famous adaptations from Leonardo DiCaprio and Robert Redford, literal A-list celebrities.
On top of all that, Japan has a famous hair wax company founded by Japanese businessmen NAMED AFTER the book.
So yes, they've heard of it because people in other countries can actually read books.