After 7J is installed in custom/everything mode, no kinput2 package is
installed.So Japanese can't be input defaultly.

In workstation installation, kinput2-canna-wnn4 is defaultly installed. 
but because Japanese convert server isn't defined when kinput2 is run.

so the file /etc/X11/xinit/xinitrc.d/xinput should be updated.

-kinput2 &
+kinput2 -canna &

#just for a try, I write the report in Japanese below
%+%9%?%`!?Everything
%b!<%I$G7J$r%$%s%9%H!<%k$7$?>l9g!"kinput2%Q%C%1!<%8$,%$%s%9%H!<%k$5$l$F$$$J$$!#%7%9%F%`$,5/F0$9$k$H!"F|K\8l$,F~NO$G$-$J$$!#

$G$b!"Workstation$r%$%s%9%H!<%k$9$k>l9g!"kinput2-canna-wnn4$,%$%s%9%H!<%k$5$l$F$$$k$,!"kinput2$N5/F0option$,4V0c$C$F$$$k$N$G!"F|K\8l$,F~NO$G$-$J$$!#
$G$b!"/etc/X11/xinit/xinitrc.d/xinput%U%!%$%k$rJT=8$7$F
-kinput2 &
+kinput2 -canna &
F|K\8l$,F~NO$G$-$k!#