To dream of Japan represents a mindset that is sensitive about positivity. You may be nervous about having things in their place or that everything is working at it should be. You don't want any problems or misunderstandings of any kind whatsoever and may be worried that something could go wrong.
Negatively, you may feel pressured into caring about something being perfect all the time. Japan could also reflect anxiety about people liking you or something you've done. Anxiety about illnesses returning or worsening.
Example: A man dreamed of being in Japan. In real life he was constantly worried that his hairloss would get worse. Japan reflected his constant need to check his hair to make sure that it wasn't falling out more.
Example 2: A woman dreamed of being in a Japanese suburb. In waking life her doctor was worried that she was going to have a miscarriage so she was order to stay home and rest. Japan in this case may have reflected her feelings of heightened sensitivity about doing whatever it took to be perfectly healthy for the baby.