if saying Sayonara and no one responds it means they will never see you Again, When saying good by to a friend one should say something like Dewa mata ne, or Jyaa mata, which is like saying see you later. If you go into a department store and you say Sayonara to the clerk, its like saying good bye i am never coming back. However, if you use a proper Dewa mata ne, it tells the store clerk you may come back and shop again.