My bad,should have say it's temporary. I think the black hair one tack back her words to keep Yuki indefintively and go back the week/month schedule they start with.Don't worry,Yuki will not stay in Chat Noir forever
The only living national treasures I'm aware of offhand are the people certified to make katanas the traditional way purely for the artistic value of the swords. First thing to show up on Google as an example is preserving the traditional pottery techniques from Japan. Wonder what that guy's thing is.