inheritance tax question

My father passed away yesterday. He was an American Citizen who lived in Yokohama with my mother on a property that was in my father's name. The house is in my mother's name. As he did not put the property in his wife's name and he is deceased, will my mother be forced to pay an inheritance tax? She lives on this property, that is a duplex and she has rentors on the second floor. She has very few liquid assets. Also, the all her children are in the U.S. and do not speak Japanese.

If there is anyone who can advise me on what she should do, I would appreciate any help.

Sincerely,

Doris

The following consultation services in foreign languages might help you.
http://www.city.yokohama.jp/ne/life/en/daily.html

If all of your father's assets passed to your mother then there is no estate tax for him. He could have passed up to $2 million in assets to other people without an estate tax. If between your parents they have assets over $2 million then you should not have all of your father's assets go to your mother (she can disclaim some to the kids). Otherwise there will likely be an estate tax when she dies.