night train to/from Hokkaido

I've seach some information from this web site and I would like to use some night train to complete my trip.
Here are my questions
1. Hamanasu express from Aomori to Sapporo , how can I book the nobi-nobi seat. If I have a sister in Japan , can she book the seat for me without payment because I will use my JR pass.
2. I will buy JR 7 days pass , in the last day I would like to take Akebono train from Aomori to Ueno. This train will arrive in the eight day, will I have to pay extras?

I 've tried JR East booking website but thier routes not cover Aomori town. I don't know why?

Hamanasu express from Aomori to Sapporo , how can I book the nobi-nobi seat.

You can make reservations at any JR station in Japan. I am not sure, but I don't think that the train books out very often outside of the peak travel seasons. In the worst case, you can ride by unreserved seat.

If I have a sister in Japan, can she book the seat for me without payment because I will use my JR pass.

No, an activated Japan Rail Pass is required to make free reservations.

I will buy JR 7 days pass , in the last day I would like to take Akebono train from Aomori to Ueno. This train will arrive in the eight day, will I have to pay extras?

No, there is a special rule that says that if you start riding the train before midnight, you can stay on board of the train beyond midnight without paying additionally.

Thank you , Uji.

If I can not book that train before I fly, which website I can check an available berth?

I have one more question.
Does JR pass cover JR bus from Samani - Erimomisaki in Hokkaido.

If I can not book that train before I fly, which website I can check an available berth?

The following website lets you look up seat availability, but it does not seem to be able to display the complete information about night trains:
http://www.jr.cyberstation.ne.jp/vacancy/Vacancy.html

Does JR pass cover JR bus from Samani - Erimomisaki in Hokkaido.

Yes, it does.

Maybe you can try this one:
http://mobile.jrhokkaido.co.jp/web/vacancy/index.asp?ar...

In case you can only read English (because I know Chinese and therefore I can recognise some of the Japanese characters on that page), this is already the page showing the seat vacanies for Hamanasu express. Unfornately, this is provided by JR Hokkaido and therefore can only show you the trains from Sapporo to Aomori, but not the other way round.

Anyway, my personal experience, I have used this train last summer. I made the booking only 1 day before I take the train and I can easily reserve a seat with my JR pass.

Hope that it can help you.