Family name for Japanese/American baby?

My wife just gave birth to our daughter here in Japan. When we married, she kept her family name. She has not yet registered our marriage in Japan (only in the US).

Now we are wondering, if we want to give the baby the (American) father's family name, will she need to register as married to me here in Japan? Currently the baby's birth certificate (issued in Japan) declares my wife's family name.

Is it possible for the baby to be registered in the US with the father's name, but be listed in Japan with the mother's family name? It seems unlikely, but we're just trying to sort this out.

Is it possible for the baby to be registered in the US with the father's name, but be listed in Japan with the mother's family name?

Yes.

As above, this is in fact a very common thing to do, you shouldn't have a problem with it. I personally know a number of half Japanese kids who have their mother's family name in Japan and their father's family name registered in Canada/the UK/Holland, so that is the name in their other passport. Some also have middle names registered in those countries, but only given name and family name in Japan.

Complications manifest itself when a marriage fails and regarding the custodial rights of father/child.

Japan will not abide by the U.S. Court ruling. And to prevent any future complications, your newborn should be registered in your koseki, not hers but in your family name, and also in U.S.

Furthermore, having registered your child under wifefs koseki will not provide a matching set of passport to the newborn.

Obviously there are potential problems when any international couples with children divorce, however the previous poster seems uninformed. Nothing she recommends will do anything for your custodial rights in the event of a divorce.

And to prevent any future complications, your newborn should be registered in your koseki, not hers but in your family name, and also in U.S.

First of all, non-japanese can't have koseki. The baby must be registered under your wife's koseki. As for the US side you will need to register the birth and apply for a social security card (and passport if you like) at the embassy. You can register the baby with whatever name you like, and it can be different than their Japanese name.

Japan will not abide by the U.S. Court ruling.

This is probably referring to the Hague Convention on the Civil Aspects of International Child Abduction, however this only apply to you if you return to the US, divorce there, gain custody, and your wife does a runner with the kids back to Japan. If you remain in Japan, however, and eventually divorce there will be no US court ruling to abide by. Also know that Japanese law currently doesn't recognize shared custody, with full custody usually granted to the mother.

Furthermore, having registered your child under wifefs koseki will not provide a matching set of passport to the newborn.

Matching passports are not necessary for international travel. In fact it is pretty normal for a dual citizens to not have matching passports, for example when their registered name differs between countries (which is exactly what the OP wants to do). But its a moot point since there is no choice but to register the baby to your wife's koseki.

Thanks for the responses!

It looks like we'll be able to do what we want in regards to her name.

Now we just have to work on not getting divorced. :D