The W124 300D Turbo was never made in RHD. The steering box would be in the direct path of the turbo's downpipe otherwise. This is why for example in the UK only non-turbo W124 300D's were sold. Never the Turbo Diesel models.

Besides, there are a lot of LHD cars in Japan. It's considered a status symbol and there's rarely any (legal) overtaking on the opposite side of the road in Japan.