Originally Posted by cockpitvisit

That link only becomes available at midnight JST three days before your visit. However, everything gets booked within minutes and the site becomes overloaded around midnight, with waiting times up to one hour, so I wouldn't hold much hope for it.

There will be another link for "same day reservations", available only after you enter the Expo site (you may have to wait a few minutes for it to appear, thanks to the glorious Expo IT ). There, you may be able to reserve something - those reservations are only available to people already on the Expo site, so they don't all get booked immediately.