I'm sorry to hear about your loss, and it always sucks when you live so far away from your family, it is unavoidable that one day you will loss some one you love without being able to say good bye to them.
Not sure about the Japanese, but the Chinese would call 91 a good and happy death in that it's a blessing to live to that age so one shouldn't feel too sad about the death. It sounded like your grandfather lived a great life and he was ready to move on to a better place. May he rest in peace.
91 years of healthy, vigorous life is an incredible blessing and, I would guess, a long life by any standard.
You’re right. He was ready to move on and he did so on his own terms. For me, I was just really hoping to introduce him in physical person to my new son at least once, and was in the process of making arrangements to do so. Unfortunately, it took longer than expected to get my son’s passport.
Thank you for your condolences.