Japanese(日本語) cannot be selected in TheMovieDB language setting
THETVDB can choose

Japanese(日本語) cannot be selected in TheMovieDB language setting
THETVDB can choose

The agent hasn’t been updated in a while and does not support all the languages available from TheMovieDB.
Could you share me the solution for updating the tmdb agent?
You can’t. This is something done by Plex.