Rust is terrible on Okinawa. Not sure on the rest of the mainland, but shouldn't be as bad. Had a miata rust out from under me while over there, but I lived in Sunabe, about 150ft from the water.

 

Yeah, most of Japan has some serious rust issues though, especially in the areas that snow a lot (Misawa area especially). Not too many locations that aren't prone to rust.

It's no secret, the Japanese don't value old ****. You could pick up a early 2000s or late 90s car for dirt ******* cheap, won't have rust that's too bad, and you could collect parts galore.

But the dream of a +25 year old car is tough man, almost a pipedream. I highly suggest having a plan B.