4-wheeler in Japan requires?

So I just shipped my 2018 Polaris Ace 500 to Iwakuni and I want to make it street legal here. Requirements?

So you shipped your 4 wheel to japan without knowing if you can make it street legal.
You can contact JAF but having this road worthy there are many aspect, such as interior, exterior and pollution regulations.

To Iwakuni? Sounds like a US Marine that didn't research ahead of himself.

I have never seen an off-road vehicle like that being driven on Japanese streets. I'm not saying it's not possible but it beggars belief that you would ship such a vehicle to Japan before even checking if it was possible to register it for street driving there. Amazing!

Before thinking about street driving, what about import permit? Did you at least research that?

Also exactly where do you want to drive with this thing? I mean, it’s not made for street driving but for kind of extreme off-road (or so it seems). Do you know where you can do such extreme off-road driving legally in Japan? Is it close enough to Iwakuni?

I have never seen an off-road vehicle like that being driven on Japanese streets.
https://www.whitehouse-orv.jp/news/20150608.php
https://www.whitehouse-orv.jp/news/20151022.php
https://www.whitehouse-orv.jp/press/20161018/
But, ACE is yet.

If you did not export it as "CDP", you would not be able to register for driving in Japan.
If not, you may drive as "IDP".
https://english.jaf.or.jp/use-jaf-more/bringin
https://english.jaf.or.jp/use-jaf-more/drive-in-japan

If you work at US MCAS base, you have to confirm that you can get "T" license plate.
BC, Japanese traffic regulations do not allow US base drivers to drive unregistered (unlicensed) vehicles on public roads.

If registration is not accepted, you can only drive on closed off-road course.

This is "Y" license plate car photo, 山口 means registered area "Yamaguchi" including Iwakuni city.
https://twitter.com/molfy_DIVA_/status/932150501952471040
"E", "H", "K", "M": U.S. military-owned non-business vehicles
"T": A privately owned vehicle, U.S. military soldiers brought from out of Japan
"Y": Vehicles other than privately owned Kei-car vehicles owned by U.S. military soldiers purchased in Japan
"A" and "B": Kei-car vehicles privately owned by U.S. soldiers purchased in Japan
(Kei?)
https://en.wikipedia.org/wiki/Kei_car