Adjust the Japanese font-family settings:

Remove Japanese names as much as possible. Since MS fonts do not have anti-aliasing, try adjusting them to use BIZ UD Fonts, which are currently considered easy to read in Japanese Windows environments.

Author: peaceroad

css/src/modules/ReadiumCSS-base.css

@@ -117,16 +117,17 @@ math {
 }
 
 :lang(ja) {
-  --RS__baseFontFamily: "游ゴシック体", YuGothic, "ヒラギノ丸ゴ", "Hiragino Sans", "Yu Gothic UI", "Meiryo UI", "MS Gothic", Roboto, Noto, "Noto Sans CJK JP", sans-serif;
+  --RS__baseFontFamily: YuGothic, "Hiragino Maru Gothic ProN", "Hiragino Sans", "Yu Gothic UI", "Meiryo UI", "MS Gothic", Roboto, Noto, "Noto Sans CJK JP", sans-serif;
 
   /* For CJK, the line-height is usually 15–20% more than for Latin */
   --RS__lineHeightCompensation: 1.167;
 
   /* Extra variables for Japanese font-stacks as we may want to reuse them for user settings + default */
-  --RS__serif-ja: "ＭＳ Ｐ明朝", "MS PMincho", "Hiragino Mincho Pro", "ヒラギノ明朝 Pro W3", "游明朝", "YuMincho", "ＭＳ 明朝", "MS Mincho", "Hiragino Mincho ProN", serif;
-  --RS__sans-serif-ja: "ＭＳ Ｐゴシック", "MS PGothic", "Hiragino Kaku Gothic Pro W3", "ヒラギノ角ゴ Pro W3", "Hiragino Sans GB", "ヒラギノ角ゴシック W3", "游ゴシック", "YuGothic", "ＭＳ ゴシック", "MS Gothic", "Hiragino Sans", sans-serif;
-  --RS__serif-ja-v: "ＭＳ 明朝", "MS Mincho", "Hiragino Mincho Pro", "ヒラギノ明朝 Pro W3", "游明朝", "YuMincho", "ＭＳ Ｐ明朝", "MS PMincho", "Hiragino Mincho ProN", serif;
-  --RS__sans-serif-ja-v: "ＭＳ ゴシック", "MS Gothic", "Hiragino Kaku Gothic Pro W3", "ヒラギノ角ゴ Pro W3", "Hiragino Sans GB", "ヒラギノ角ゴシック W3", "游ゴシック", "YuGothic", "ＭＳ Ｐゴシック", "MS PGothic", "Hiragino Sans", sans-serif;
+  /* BIZ UD fonts will work on Windows. If you set half-width (ASCII) characters to `upright` using `text-orientation`, the width of these characters remains narrow. In this case, specify `font-variant-east-asian: full-width;` as well. */
+  --RS__serif-ja: "Hiragino Mincho ProN", "Hiragino Mincho Pro", "YuMincho", "BIZ UDPMincho", "Yu Mincho", "ＭＳ Ｐ明朝", "MS PMincho", serif;
+  --RS__sans-serif-ja: "Hiragino Sans", "Hiragino Kaku Gothic ProN", "Hiragino Kaku Gothic Pro", "ヒラギノ角ゴ W3", "YuGothic", "BIZ UDPGothic", "Yu Gothic", "ＭＳ Ｐゴシック", "MS PGothic", sans-serif;
+  --RS__serif-ja-v: "Hiragino Mincho ProN", "Hiragino Mincho Pro", "YuMincho", "BIZ UDPMincho", "Yu Mincho", "ＭＳ明朝", "MS Mincho", serif;
+  --RS__sans-serif-ja-v: "Hiragino Sans", "Hiragino Kaku Gothic ProN", "Hiragino Kaku Gothic Pro", "ヒラギノ角ゴ W3", "YuGothic", "BIZ UDGothic", "Yu Gothic", "ＭＳゴシック", "MS Gothic", sans-serif;
 }
 
 :lang(km) {