I too am assuming that the cruise is from Yokohama at the pier at Osanbashi. Coming one day before doesn't leave a lot of time for sightseeing, but I would recommend going to Yokohama -- conditioned on the time of arrival. Even though it is not "traditional" Japan, the Minato Mirai area around the pier is in of itself a modernistic tourist destination. Osanbashi itself is shaped like the back of a whale.
Enjoy your one day, and your cruise.