Looks like an encoding issue. Did you make sure that the tab delimited input file was utf8 encoded?
B̶T̶W̶,̶ ̶y̶o̶u̶ ̶c̶a̶n̶n̶o̶t̶ ̶c̶r̶e̶a̶t̶e̶ ̶J̶a̶p̶a̶n̶e̶s̶e̶ ̶l̶o̶o̶k̶u̶p̶ ̶d̶i̶c̶t̶i̶o̶n̶a̶r̶i̶e̶s̶,̶ ̶b̶e̶c̶a̶u̶s̶e̶ ̶
t̶h̶e̶ ̶K̶i̶n̶d̶l̶e̶ ̶d̶i̶c̶t̶i̶o̶n̶a̶r̶y̶ ̶w̶o̶r̶d̶ ̶s̶e̶g̶m̶e̶n̶t̶a̶t̶i̶o̶n̶/̶l̶o̶o̶k̶u̶p̶ ̶c̶o̶d̶e̶ ̶o̶n̶l̶y̶ ̶s̶u̶p̶p̶o̶r̶t̶s̶ ̶L̶a̶t̶i̶n̶ ̶1̶ ̶b̶a̶s̶e̶d̶ ̶c̶h̶a̶r̶a̶c̶t̶e̶r̶s̶.̶
EDIT: The latest firmware update fixed this issue and Kindle Paperwhites sold in Japan come with Japanese dictionaries.
According to
this post, Kindles sold in Japan come with the Progressive Eiwa Chuujiten English-to-Japanese dictionary and the (monolingual) Digital Daijisen dictionary.