Unlike the US, Japan is a righthand drive country, meaning that the driver sits on the right side of the vehicle, and the vehicle drives on the left side of the road.
Now, all minitrucks sold by Minitruck World are sold for off road use only, so the fact that you will be driving from the opposite side of the vehicle is not going to have any highway safety implications -- such as being able to have good visibility at junctions, being able to see around vehicles when deciding whether to overtake or not etc. -- because you will not be using your minitruck on regular streets anyway.
When driving off road, you'll find that the excellent driving position, great visibility, standard mirrors, headlights and windshield wipers all work together to give you the great visibility you need to maneuver the minitruck easily.
Sure if you have no experience driving from the "wrong" side of the vehicle, you may want to do some practice in a more open area first -- and that's especially true if you get a manual model and need to get some practice in using your left hand to change gears.
But it's really not that difficult. Don't believe me? Just think about the over 3 million tourists from the UK that visit the US each year. They arrive blurry-eyed and jet-lagged from a righthand drive country, jump in a lefthand drive rental car, and zoom off to their hotels with half-asleep kids screaming in the back. Yes, all the controls are around the "wrong" way for them and the rules of the road are quite different. Yet you never hear stories about a seasonal slaughter on Florida's roads because of clueless UK tourist drivers.
If a huge number of jet-lagged British drivers can switch from RHD to LHD and deal with different driving rules without incident each year, you can be sure that you will be able to adapt to the driving position in your minitruck with a little practice in a short amount of time.