There is an incredible Volvo scene in Japan, and as has been mentioned, Japanese people are very kind to their cars. Add to that that 240s were never used as workhorses in Japan like they were here - instead they were expensive premium imports - and you have a recipe for a lot remaining. When I lived in Japan as a student the number of classic/interesting cars I saw every day blew my mind.
I'll be moving back to Japan next year for work after I graduate and will, of course, find myself a JDM 240. I have my eye on this one
http://cocsun.jp/sell/cat79/244gl.php