UK Citizen visiting Japan then taking an Asian cruise

I am an UK citizen and will be taking a cruise from Japan which has a stop in Shanghai. Do I need a visa for a 24 hour stop and can the cruise line do this? If not, I will need to obtain the entry permit in either Tokyo or Osaka prior to boarding. Can it be processed in a day and if so, where do I start? If I can't get it, can I still board the ship and just stay on board at Shanghai?
Thank you for any assistance....