Maru-Gothic or rounded sans-serif is one of well established and popular typeface categories in Japan. I see ui-rounded in CSS Font 4 but not generic "rounded". I believe the rounded version of sans-serif is pretty generic across different scripts.
Apple's platforms have the rounded sans-serif. However Windows does not have the typeface, the Office has it, i.e. effectively most if not all Windows users in Japan has it.
Commenting on https://github.com/w3c/i18n-discuss/wiki/Generic-font-families
Maru-Gothic or rounded sans-serif is one of well established and popular typeface categories in Japan. I see ui-rounded in CSS Font 4 but not generic "rounded". I believe the rounded version of sans-serif is pretty generic across different scripts.
Apple's platforms have the rounded sans-serif. However Windows does not have the typeface, the Office has it, i.e. effectively most if not all Windows users in Japan has it.