Is it possible to reserve a seat for the train which will set off a few hours later

Hi there,

It may be possible since the 20th is on a Monday, still night trains are always very popular and it can be hard obtaining a reservation at any time. The nice thing about the Hamanasu is that it always has a couple of cars with non-reserved seats. So it case everything sells out you can still get a seat but you have to come to the station at least an hour to line up for the train and beat the other crowds.

Still I would recommend making a plan B, just in case things don't work out.

You can see seat availability on this website, unfortunately it is only in Japanese but if you put 青森 (Aomori) in the first field and 札幌 (Sapporo) and select the lowest option at お乗りになる列車 (3rd field) that you can see seats available for your selected train.

Feel free to post here again around the time that you travel and I can check it for you!
-Daniel