My friend and I are arriving in Japan only 12 hours before our first schedule train, the Akebono night train from Tokyo to Aomori, and we have purchased JR Passes so the Goron-to-shito should be free but thing is we can't reserve our seats until we arrive and we actually go to a JR office.
Is there a way to get around this problem? Should we even worry or would a seat like that in a train like that on May 24th be booked out 12hours before it leaves?