\ltj@safe@num@or{nil}{#1},\ltj@safe@num@or{nil}{#2},#4,#5)}}
% jatextfont = {<char_code>, <font_cs>}
\define@key[ltj]{japaram}{jatextfont}{%
\ltj@safe@num@or{nil}{#1},\ltj@safe@num@or{nil}{#2},#4,#5)}}
% jatextfont = {<char_code>, <font_cs>}
\define@key[ltj]{japaram}{jatextfont}{%