I arrived in Akita early in the morning on the ferry from Tomakomai, Hokkaido., where I had been traveling for a month. Recently there was a large earthquake in Hokkaido so trains had been canceled and other public transport (such as the ferry) became crowded.
However, it was still easy for me to get a ticket without a reservation because of the size of the boat. I bought the cheapest fare which still gave me a fairly comfortable bed for the overnight ride and cost around 5000 yen; much cheaper than most forms of transport, since the main income of these ferries comes from shipping goods.
I don’t usually get seasick but I think it would be hard to get seasick on ferries of this size; conditions were fairly rough but I couldn’t feel any movement.