I'm.not sure, no, but loads of people tow stuff using import 4x4s over here. The police wouldn't even bother to look unless they saw you towing something that they thought might take you over the limit, in which case they might pull you over and start asking questions, but I can't see them pulling you over on the off chance just to check if your car has a stamped up plate on it!
I think it's just the trailers that must say have a plate saying what their load capacity is, etc. not the tow car.
Find out the specs on line, print them off and take them with you?
Or if they ask, just point them at a sticker that's all in jap and tell them that's the load sticker and they're welcome to translate!
