The currently installed Japanese fonts for rendering SVG file to PNG image are Kochi Mincho (serif) and Kochi Gothic (sans-serif). The Western/English characters differ correctly in these 2 fonts, but the actual kanji, katakana and hiragana are not. All three syllabaries look exactly the same in the form of sans-serif typeface (Gothic). There could be some problem with the Kochi Mincho font installed on Wikimedia.
Please check this image and scroll to the Kochi fonts row for inspection:
P.S. I tested the fonts with Jarry1250's SVG Check on wmflabs which correctly renders text of Mincho font in serif typeface.