First, copy the Japanese text into MS Word. Use MS Mincho font, with font size of 12pts or bigger, and bold the text (this is important, because without it, characters becomes too faint to read clearly in Sony Reader).
Use the Page Setup settings and PDF printer settings described in the User’s Guide to create PDF documents for the Sony Reader. Then, save Japanese text files as PDF file by sending to PDF printer.
You can view the saved file in Sony Reader directly, but up to a certain maximum file size (about 40 pages?). Anything beyond that, the screen will be blank when you open the file in Sony Reader. This limitation appears to be due to the big size of the Mincho font embedded in the PDF file.
In order to circumvent the file size limit, you can save the PDF file as image files (JPEG) using Adobe Acrobat. The file will be split into a number of image files with numbers running in sequence. You can combine these separate image files back into a PDF by right clicking the first image file, and selecting “Combine in Adobe Acrobat….”. When the dialog box appears, you go to browse, and select the remaining image files, and press O.K.
The resulting image may not be as clear as the original text. Conversion to image files somehow produces slight gray smears round the character, giving them a look of old text. I rather like the effect!