Google's market share in Japan is low - about 35%. And in addition the Japanese don't really bother learning English, so don't search using English keywords either.
What you are probably seeing is the underlying SERPs unmodified by user-feedback simply because the locals arn't searching those terms.
P.S. User-feedback is becoming bigger in the main SERPs - I backspaced into the search results the other day, and the "block xyz site" message flashed in red before fading to blue. My first reaction was "what was that", because all I registered was a flash of red, so I performed the action again to see what it was. G is really trying to get the attention of Chrome users to get them to feedback.
P.P.S. The intent of a searcher in English is different from the intent of a searcher in Japanese.
Try the following experiment: perform your search in english. Then translate your keyword into Japanese using Bablefish [babelfish.yahoo.com], and paste the kanji into the google.jp searchbox and search again - the results will be completely different - the urls returned are mainly .co.jp
So the English language search results on google.jp are just there for those few expats who search in English, and their numbers are so low as to not really be able to affect and modify the underlying SERPs the way users in the USA can, for instance.
It's interesting though isn't it? It suggests that Pandalisation is driven by users.