The main Japanese brands, Toyota and Honda, suffered from huge supply chain issues due to the earthquake and tsunami, plus their designs are just flat out boring. The Koreans, Hyundai and Kia, have cars that are rivaling the Japanese on quality and have a little bit of design flair, plus they were available. Given all that, there is no surprise sales for the Koreans are way up.
Last year I was ready to retire my 3rd Honda after 15 years in the '95. Ended up giving it to my relatives for their teenagers to learn on a stick. The 18yo male has already trashed it (sniff).
I had been hankering for the Honda Euro-Diesel but then the California CARB regs made Honda rethink. I am now in an Audi(VW) TDI A3 and loving it. 28mpg city and 40+ highway and no problems with limited range or fuel availability.