! Package inputenc Error: Unicode character ^^H (U+0008) - latex

Question

I installed MacTex from brew brew install mactex-no-gui --cask
test.tex
\documentclass{jarticle}
\usepackage{amsmath,amsfonts}
\begin{document}
mytest--m=testmode テストを行う
\end{document}
I try to compile this this simple text with platex
It shows this error.
I guess it is related to unicode setting ??
because I put some Japanese character in it.
How can I fix it?
$platex test.tex
This is e-pTeX, Version 3.14159265-p3.8.3-191112-2.6 (utf8.euc) (TeX Live 2020) (preloaded format=platex)
restricted \write18 enabled.
entering extended mode
(./test.tex
pLaTeX2e <2020-02-02>+3 (based on LaTeX2e <2020-02-02> patch level 5)
L3 programming layer <2020-03-06>
(/usr/local/texlive/2020/texmf-dist/tex/platex/base/jarticle.cls
Document Class: jarticle 2020/01/03 v1.8e Standard pLaTeX class
(/usr/local/texlive/2020/texmf-dist/tex/platex/base/jsize10.clo))
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsmath/amsmath.sty
For additional information on amsmath, use the `?' option.
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsmath/amstext.sty
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsmath/amsgen.sty))
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsmath/amsbsy.sty)
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsmath/amsopn.sty))
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsfonts/amsfonts.sty)
(/usr/local/texlive/2020/texmf-dist/tex/latex/l3backend/l3backend-dvips.def)
(./test.aux)
! Package inputenc Error: Unicode character ^^H (U+0008)
(inputenc) not set up for use with LaTeX.
See the inputenc package documentation for explanation.
Type H <return> for immediate help.
...
l.6 mytest^^H
--m=crond テストを行う