The ferry from Kagoshima at the south of mainland Japan to Okinawa leaves at around 5.30pm to 6.00pm which is a good number of hours after the checkout time of most accommodation.
I know from experience that many ferry terminals in Japan have free Wi-Fi and seem to recall some having power outlets available though all over Japan it's common to see power outlets that need a special plug, have covers over them, or have little signs saying they're not for public use.
The name of the terminal is Amami Okinawa Ferry Terminal (奄美・沖縄フェリーターミナル) and the only websites I can find are for the two ferry companies that operate there, not for the terminal itself: A Line, Marix Line. Both websites have little or no English. The A Line site tells me there is Internet on the ferry itself but I can't find anything about the Marix ferry or the terminal building on either site.
Does anybody know from experience of from superior web search skills?