Kevin on "[Theme: Virtue] How to set Japanese font up "メイリオ(Meiryo)"?"

If your language in your html is "lang="ja", then this CSS should work if you place it into Appearance> Theme Options> Advanced Settings.

html[lang="ja"] body, html[lang="ja"] body p, html[lang="ja"] h1, html[lang="ja"] h2, html[lang="ja"] h3, html[lang="ja"] h4, html[lang="ja"] h5, html[lang="ja"] a { font-family: "Meiryo" !important;
}

If that doesn't work, post a link and I'll adjust it accordingly.