Just add woff2 font files into your CSS.
Including the following fonts,
-
Source Han Sans JP Normal
-
Source Han Sans JP Heavy
-
Source Han Sans JP ExtraLight
Other weights can be found in this repo.
https://github.com/adobe-fonts/source-han-sans
https://github.com/google/woff2
No license for this repo. License of Source Han Sans is SIL Open Font.