JR pass overnight

I�fve a plan to take overnight train from Aomori to Tokyo, I won�ft book a couchette I�fll take a normal seat (Limited Express Akebono) on 22 night of June whereas my jr pass is on 7th day(its expiry date is on 23 June 00:00) Can I use JR pass until I arrive in Tokyo on 23 June or I need to pay extra money ?

I�fll take a normal seat (Limited Express Akebono)

The Akebono does not have normal seats! But it has so called goron to shito compartments, which can be used without supplement by pass holders, but require advance reservations.

on 22 night of June whereas my jr pass is on 7th day(its expiry date is on 23 June 00:00) Can I use JR pass until I arrive in Tokyo on 23 June or I need to pay extra money ?

If you successfully make a reservation, the trip will be fully covered.

I have no trouble booking the Akebono night train out on my few previous trips. However, there were times when the snow was really bad, the train from Aomori were cancelled.
I had this experience on 2009 Dec. When that happen, you have to pay extra from Aomori to Tokyo the next day as your JR pass won't be valid the next day.

Japan Rail Pass: Notes regarding use:
http://japanrailpass.net/eng/en008.html

I've a plan to take overnight train from Aomori to Tokyo

Southbound Akebono trains are destined not to Tokyo Station, but to Ueno Station in Tokyo.

Can I use JR pass until I arrive in Tokyo on 23 June?

Yes, as long as you take the Akebono train from 22 through 23 June.
(See No.6 of the first chapter of the Notes.)
To get this ride wholly covered by your 7-day JRP, you have to be both within the railroad network and on the train when the 7 days end.

lester:
when the snow was really bad, the train from Aomori were cancelled.
When that happen, you have to pay extra from Aomori to Tokyo the next day as your JR pass won't be valid the next day.

Yes, at least a Ltd. Express surcharge is required in that case.
If the staff has okayed your staying over the night in the station, the basic fare can be covered by your JRP.
The surcharge is 6300 yen for a Shinkansen Hayete ride on a reserved seat from Shin-Aomori to Tokyo on 23 June.
(See also �gAlso no refund or extension�c�h in No. 4 of the second chapter.)