Okay, so your manuscript takes place in Japan. How many readers do you think will understand Japanese? Even more importantly, how many of those readers do you think will have the patience to put up with a book written partially in another language?
Congratulations, you speak Japanese: a difficult language. Guess what? Most of the rest of us don't understand it. Oh, you knew that, so you put the translations in parentheses after each sentence? Guess what? Books don't use subtitles.
A quick and easy way to alienate readers is to put dialogue in another language. Okay, so let's say the story takes place in France. You want the reader to know the main character can speak the language. You can easily fix that by writing, "Your fly is unzipped," main character said flawlessly in French. The man replied in his native tongue, "Why are you looking at my crotch?"
Confusing the reader is a fatal mistake. Alienating them by writing things they can't understand isn't much better.