Most people are inherently good. It's just some may have 'gone bad'. People are shaped by their experiences, upbringing and natural brain chemistry. We all start out 'good' I should imagine, or rather a blank canvas for 'something' to be painted on.
Nothing is our fault per se as we didn't have the choice as kids, but as adults it is our responsibility to learn, grow and do the right thing. This is always subjective, and it could be argued that everyone is always doing what they believe is right in a given moment... which may well differ from others (who would probably act in the same way, given the same set of circumstances).
So, all in all, good in essence but heavily influenced and conditioned by society, media, family, school, work etc... so may make short-term bad judgements... but generally aware and always want to get back to the 'good side'.
Anger, for example is never about the other person, it's about the person with the anger and their frustrations. We all need to relax and play our own game... easier said than done!
Enjoy Japan! :)