In the movie Isle of Dogs most of the human characters speak Japanese. Was it real Japanese language, or was it only some mumbling pretending to be Japanese or some funny lines that only a Japanese-speaking person would understand?
The Japanese is 'real' for a slightly distorted version of 'reality'.
It is sometimes muffled, sometimes a little stilted and some of the signage is a little awkward.
I have a Japanese friend who saw it at the time and pointed some of this out to me, but I found a written reference to it on Vulture: What It’s Like to Watch Isle of Dogs As a Japanese Speaker
Some extracts from the above ref...
For what it’s worth, the spoken Japanese made complete sense, there was no accent or awkwardness
The main [Japanese-speaking] characters, or anyone with relatively more dialogue, like Atari or Major-Domo, sounded a bit weird. They didn’t try to speak Japanese precisely, but they had a Japanese ‘cultural effect.’ So it was kind of caricatured.
The written language, as it appears in the art direction and onscreen text, stood out more than the un-subtitled dialogue. “A lot of it was an awkward, kind of choppy phrasing. It kind of made me think that someone had thrown these English phrases into Google Translate. The [characters] weren’t the exact characters you would use in that context."