The only Japanese car designer I have been able to find with a last name that starts with a W, is Audi's Satoshi Wada. Something tells me he isn't the guy, and obviously this design isn't a new creation. When you said Masao, I thought of racing car designer Masao Ono, but I haven't been able to find any information on a road car design from his pen - or, indeed, any mention of a career in the US building up another car brand.
Any more clues to give away?