This happens when you apply HiraKakuStd W8 to text outside its character set (e.g., Simplified Chinese or Korean). The missing glyphs appear as squares. Always check encoding (UTF-8) and stick to Japanese JIS characters.
“Hiragino Kaku Gothic has a design concept of being 'cool and contemporary' while remaining orthodox and universally preferable with excellent readability.” Adobe Fonts hirakakustd w8 font
: Versions of this font have historically been bundled as standard system fonts on macOS and iOS , making it a staple of the Apple design aesthetic. This happens when you apply HiraKakuStd W8 to