unhbox and unvbox not supported?

[yuishin-kikuchi]

I found unhbox and unvbox are not supported.
I think these are very important.

(LuaHBTeX, Version 1.17.0 (TeX Live 2023)) + lua-ul [2022-05-31]

\documentclass{article}

\usepackage{luacolor}
\usepackage[soul]{lua-ul}

\begin{document}
Inside underLine / strikeThrough / highLight,
unhbox and unvbox are not affected by the command.

\underLine{This is a test: \setbox0\hbox{abc}\unhbox0, \setbox0\vbox{abc}\unvbox0, OK?}

\strikeThrough{This is a test: \setbox0\hbox{abc}\unhbox0, \setbox0\vbox{abc}\unvbox0, OK?}

\highLight{This is a test: \setbox0\hbox{abc}\unhbox0, \setbox0\vbox{abc}\unvbox0, OK?}

\end{document}

[yuishin-kikuchi]

Uggh... if I could solve this problem...

\documentclass{article}

\usepackage{luatexja}% package for Japanese support
\usepackage{pxrubrica}% package for Japanese ruby support, using \unhbox
\usepackage{luacolor}
\usepackage[soul]{lua-ul}

\begin{document}
日本人でも\highLight{漢字で「\ruby[g]{薔薇}{ばら}」を書く}のは難しい。\par
It is difficult to \highLight{write \textit{bara}, which means rose, in Kanji} even for many Japanese.\par
\end{document}

I know a quick solution is to use \mbox.
But this solution has a problem of line break.
Any better solutions?