I have same problem when searching question or answer in japanese. Like chinese, japanese sentence has no space between words.
Gidgreen gave us a clue to deal with such kind of problem inserting space between characters so it can be splitted into words .But I still have trouble with this. My site is not pure japanese, It mixes between Japanese and Vietnamese (separates words by space like English). For example, sometime i got a question like this: [ Vì sao người Nhật không nói 愛している ?] or [にあずからなかった cấu trúc này là như nào vậy] . In this case, the solutions does not work well, because it may change vietnamese word into splitted characters like this: không ---> k h ô n g
Have you got any idea to deal with this?