One of the many decisions I had to make in writing Getting Oriented was how to handle the Japanese language. I knew I didn't want to provide instant translations that you sometimes see, something like: "Ichiro picked up his hashi [chopsticks] and dug into his katsudon [bowl of rice and pork]."
My answer: When a character is speaking Japanese, the text is in italic. It becomes a little awkward sometimes when the characters are switching from Japanese to English and back, but I believe readers can follow.
As a result, there are almost no Japanese words in a 240-page book set in Japan. I did leave a few: moshi moshi, which I trusted most readers to understand from the context; sokaiya and dotera, for which there are no good English equivalents, and which I explain as soon as I use them. Toward the end of the book, my tour guide begins to tell a Japanese joke in Japanese, but when his American guests demand to hear it in English, he beings again in English.
To show that this is a novel about Japan, however, I did use Japanese at the beginning of each chapter:
第一章、第二章 etc. and I've been asked what it means.
It says "Chapter 1," "Chapter 2," etc. My way of giving a genuine Japanese flavor to the novel.