The decklist will have a column for set and number so can be checked.
I can see why if you have a large number of japanese cards in your deck it might be sensible to write the japanese names down. But I suspect that many will just assume you are being a smart-***.
If you were playing at one of my events (and I'm sure I speak for many, many TOs), you would need to refer to the cards by their English card names on your decklist.
That's exactly what I did in Manchester CC: I wrote a version of the decklist in English and another one in French, as I'm playing loads of French cards.
But NoPoke is right, it just sounds a little... conceited... But I am, so I don't care ^^"