It's possible to find true pixel/bitmap Japanese fonts but they're often in old FONTX2 format, and difficult to convert.
Luckily a kind soul in Japan has already converted the most common bitmap fonts! Here bitmap data has been converted to TTF outlines.
To convert from TTF strokes back into real bitmap data:
Use of Caps to do this has not been verified.
This set of Japanese bitmap-style fonts is very comprehensive (all fonts support Kanji up to JIS Level 2, some to level 4) and also OK for commercial use and re-distribution! (various licences)
(sizes range from 10px to 24px)
At the bottom of the page http://jikasei.me/font/jf-dotfont/ there are some fonts that have different licence terms that are not free for commercial use (eg. Elisa, a very famous 8x8 font). These are not shown on this page.
Also this set of serif Japanese bitmap-style fonts under SIL Open Font License 1.1 (so OK for commercial use)
(sizes to 12 to 32px)