Recently I wrote a journal about "English literature".
I got a message from a graduate student, who is majoring in English literature. In this message she told me that "English literature" basically meant literature written in the English language.
Now the backgrounds of authors of English literature are quite various, and the diversity of them gives English literature fertility. For example, Salman Rushdie, V. S. Naipaul and Kazuo Ishiguro. But when you think of James Joyce, Vladimir Nabokov and Joseph Conrad, you will find that it is not new that English literature has diversity.
Nowadays in Japanese literature there are authors, who are non-Japanese native speakers, for example Hideo Levy (リービ英雄) and Yang Yi (楊逸). Lu Xun (魯迅) wrote in Japanese, so it is not new in Japanese literature, either.
When modern Japanese literature was established in the Meiji era, most authors were quite good at European languages. Soseki Natsume (夏目漱石) had been a scholar of English literature before he began to write novels. Ogai Mori (森鷗外) was famous for his translation of European poems. Koyo Ozaki (尾崎紅葉), who is thought to have written traditional Japanese novels now, read many western novels and used their plots for his novels. Before the Meiji era, Japanese literature had poems and stories but no modern novels, so they eagerly studied western literature to create modern Japanese literature and modern Japanese prose.
It is said that the first modern Japanese prose was written by Shimei Futabatei (二葉亭四迷). It was a translation of Ivan Turgenev's short story. When he wrote a novel, he wrote it in Russian first and then he translated it into Japanese.
Soseki Natsume was familiar with English literature, classic Chinese literature and classic Japanese literature. He tried to make up a universal theory of "world literature", when he studied in London. Finally he failed to make up it, but I think that he might have tried to create novels of "world literature".
Modern Japanese literature and prose were deeply influenced by western languages, in other words, they can be said to be based on western languages. In the first place Japanese prose is based on classic Chinese. We cannot think about Japanese literature and language without influences of foreign languages.
Japanese literature is relating to foreign literature and languages now. Haruki Murakami is deeply influenced by American literature. His first novel "Hear the Wind Sing" almost seems to be a translation of a Kurt Vonnegut novel. Now his novels influence literature all over the world through translations into many languages. They became the "world literature", which Soseki Natsume tried to create.
Yoko Tawada (多和田葉子) wrote novels in Japanese and in German at the same time. She creates new Japanese literature and German literature through doing so.
I guess that the same thing happened in many other languages. Before the Russian Revolution, the Russian nobility spoke the French language and read French literature. I don’t know about the history of Russian literature and language, but I think that French literature and language might have influenced Russian literature and language, just as Russian literature and language influenced Japanese literature and language. And then Russian literature, for example Dostoyevsky, Tolstoy and Chekhov, spread all over the world through translations.
Languages cross over each other, and literature is basically multilingual.