Many people who is living abroad especially United States told me that I should not say sorry so easily. Actually I found several blogs that said almost same thing but I try to re-think about this issue.

I, personally, think it could be better to say sorry if you want to continue relation. Expressing your apology will make people peaceful rather he or she considers to sue if one say sorry.

But those blogs said if you say sorry means you admit your ERROR, means you may be sued or fired, means you may be redressed suit.
Yes, I understand if you are in a court case. If you admit something and say sorry makes you millions of dollars compensation, you should not say sorry only for maintaining relation.
In case you are in a traffic accident, the cause may be "not looking ahead carefully" for you and "speeding" for the other side, also you should not say sorry only for maintaining atmosphere.

I agree those art of saying sorry is one of technical issues for negotiation.
I think both should say sorry to maintain atmosphere in such conflict.
That maintains atmosphere and start of negotiations are same.

In addition, I would like to describe here about "yuzuri-ai" spirit in Japanese.
In Japanese-English dictionally, some expresses it as "give and take".
It's almost near, but core of its feeling is different.
My understanding is "Give and take" means "you give to take". I truly think it is fair.
But Japanese "yuzuri-ai" is "just you give, then you may be given but it is not noblesse if you want to take".

You can give but the other can not give sometimes, but you allow it. That will help you when you can not give.
If you only get without giving, other will loose things to give you finally, so you should give when you become to give others. That will make "yuzuri-ai" spiral.

Japan provides huge amount of ODA for many other countries.
The basic mind of this behavior is we believe "yuzuri-ai" will make world peace.
Sometime in the future, someone will give help to whom someone gave thing in the past.

UN decided for North Korean missile issue to announce the statement, but not resolution.

I love this japanese style "giving without expecting taking".

But we may be not able to give continuously without getting, because nobody plays "yuzuri-ai".