A long time ago, Japan was very poor and it was difficult to get any food. Since then, they have always been grateful to have something they can eat.
When you leave one piece of rice, Japanese old people say “You will go blind”. After meal, they even drink Green tea with their bowls, that they had rice in, not to waste any rice or taste.
When you eat, you should not put your elbow on the table nor put your bowl on the table while you are eating. It doesn’t look respectful and people think you’re like an animal by not using both hands (this doesn’t occur in European food with knife and fork).
Also when someone’s giving you food with chopsticks, you cannot take it with chopsticks (it’s called “Hashi-watashi/Awase-bashi”). You can receive it with your plate, or you can take it from his plate, but never touch someone’s chopsticks with yours. This is because when someone died, in Japan, they pick up his bone with special chopsticks and carry it to next person until its urn.
When you get complimented by someone, you should be modest and deny even though you are thinking it’s right.
When someone offers you something, you should deny once even though you really want it. Most importantly, you should not forget about it and you will offer something to him next time.
In Japan, people bow when they say Hello, Good bye, Thank you, and Sorry, but not with hands together. We put hands together when we apologise or ask for a favour but not with a bow. Some foreigners get confused with other asian culture(ex: Thailand or India) and bow to Japanese with hands together, but this is not quite Japanese way. We bow with hands together when we pray.
They always respect others and be thankful, and never look down on people. This is how Japanese people live with others, because no one can live alone.
They believe that everyone needs help and this world is about give and take.