Honestly, I don't know. If I was in your situation I'd want more proof than what I have given you. Can anyone else with more knowledge than me of how businesses in Japan work find anything on this company.?
How can you tell? I see they list Morita Motors on their banking information page but they don't say anything about ownership. Maybe Morita Motors is just a local partner. Anyway I would suggest calling both offices, asking for information about buying a car including the relationship between Morita Motors & Universal Motors to help judge if it's legitimate or not. I find it odd that Universal Motors is supposedly based in Germany yet they don't offer German as a language on their web site.
Also the domain name was only registered two years ago from Pakistan. They claim to be part of Consortium Elit (also only registered two years ago) but this web site is very basic with only generic content and seems to be registered out of Kazakhstan.
I feel a little comfortable about Morita Motors but I feel suspicious about Universal Motors / Consortium Elit.