Camping in Japan and reserving last minute

Hi everyone,

It's my second time in Japan and I just went up north down to Tokyo. Visiting major cities and stuff. I'm going back to Tokyo for a few days to meet some friends again. But after that I have a week left and was thinking of renting a camper van and do a 5 day trip.

I did some research and on every website of the campsites I see it's quite popular. Has anyone did a camper van trip out of Tokyo, would you mind sharing your itinerary? But is it ok to reserve last minute and how busy is it during the week at those campsites. Thinking of going next week.

Thanks for the replies!