I've posted the first public version of the Tsukurimashou parametric font family on my Web site at http://ansuz.sooke.bc.ca/entry/160.
The main goal of this project is to support my own study of the Japanese language, so the finished product is less important than the process of getting there. However, you might still enjoy looking at it. To my knowledge, there's never been a native MetaFont family with glyph coverage for Japanese; there exist a couple that are conversions from other formats, and there was also the Quixote Oriental Fonts Project, announced more than two decades ago, apparently never usable, and now long abandoned.
Tsukurimashou is free under the GNU GPL 3 with font-embedding clarification. MetaFont (actually MetaType1) sources for six styles are in the package, along with precompiled OTF files for two of those. Current glyph coverage is Latin-1, hiragana, and katakana, but bear in mind that as it's specifically designed for use with Japanese, the Latin alphabet is not my main priority. The Latin is monospaced, to go with the monospace CJK characters. Having the kana allows these fonts to be used basically to write Japanese at a kindergarten reading level; I'm just at the point where I can start adding kanji, which is where the real fun will begin. I'd really like to make it work with vertical typesetting, but it currently doesn't.
There are also a few extra goodies, like my previously-released Genjimon fonts, included in the package.