\ProcessKeysOptions{ luatexja-fontspec }
\RequirePackage{fontspec}[2017/01/01]% v2.5c
-\RequirePackage{luatexja-fontspec-26h}
+\@ifpackagelater{fontspec}{2018/07/29}%
+ {\RequirePackage{luatexja-fontspec-26h}}% v2.6h
+ {\RequirePackage{luatexja-fontspec-25c}}% v2.5c
\ExplSyntaxOff
%%%%%%%% Now we completely ignore kanjifont definition file.