How about using what Word calls a "vertical text box":
Using xml Syntax Highlighting
<w:r>
<w:rPr>
<w:noProof/>
<w:lang w:eastAsia="ja-JP"/>
</w:rPr>
<w:pict>
<v:shapetype o:spt="202.0" path="m,l,21600r21600,l21600,xe" coordsize="21600,21600" id="_x0000_t202">
<v:stroke joinstyle="miter"/>
<v:path gradientshapeok="t" o:connecttype="rect"/>
</v:shapetype>
<v:shape o:gfxdata="UEsDBB...QYAAAAABAAEAPMAAAD1BQAAAAA=" type="#_x0000_t202" style="position:absolute;margin-left:31.5pt;margin-top:51pt;width:69pt;height:80.25pt;z-index:251659264;visibility:visible;mso-wrap-style:square;mso-wrap-distance-left:9pt;mso-wrap-distance-top:0;mso-wrap-distance-right:9pt;mso-wrap-distance-bottom:0;mso-position-horizontal:absolute;mso-position-horizontal-relative:text;mso-position-vertical:absolute;mso-position-vertical-relative:text;v-text-anchor:top" id="Text Box 1" o:spid="_x0000_s1026" strokeweight=".5pt" fillcolor="white [3201]">
<v:textbox style="layout-flow:vertical-ideographic">
<w:txbxContent>
<w:p >
<w:r>
<w:t>Hello
</w:t>
</w:r>
</w:p>
</w:txbxContent>
</v:textbox>
</v:shape>
</w:pict>
</w:r>
Parsed in 0.002 seconds, using
GeSHi 1.0.8.4
or the other direction (notice "rotation:180"):
Using xml Syntax Highlighting
<w:r>
<w:rPr>
<w:noProof/>
<w:lang w:eastAsia="ja-JP"/>
</w:rPr>
<w:pict>
<v:shapetype o:spt="202.0" path="m,l,21600r21600,l21600,xe" coordsize="21600,21600" id="_x0000_t202">
<v:stroke joinstyle="miter"/>
<v:path gradientshapeok="t" o:connecttype="rect"/>
</v:shapetype>
<v:shape o:gfxdata="UEsDBBQABgAIAAAAIQ...eG1sUEsFBgAAAAAEAAQA8wAAAAYGAAAAAA==" type="#_x0000_t202" style="position:absolute;margin-left:31.5pt;margin-top:51pt;width:69pt;height:80.25pt;rotation:180;z-index:251659264;visibility:visible;mso-wrap-style:square;mso-wrap-distance-left:9pt;mso-wrap-distance-top:0;mso-wrap-distance-right:9pt;mso-wrap-distance-bottom:0;mso-position-horizontal:absolute;mso-position-horizontal-relative:text;mso-position-vertical:absolute;mso-position-vertical-relative:text;v-text-anchor:top" id="Text Box 1" o:spid="_x0000_s1026" strokeweight=".5pt" fillcolor="white [3201]">
<v:textbox style="layout-flow:vertical-ideographic">
<w:txbxContent>
<w:p >
<w:r>
<w:t>Hello
</w:t>
</w:r>
</w:p>
</w:txbxContent>
</v:textbox>
</v:shape>
</w:pict>
</w:r>
Parsed in 0.002 seconds, using
GeSHi 1.0.8.4
Generate corresponding code using the Word AddIn.