I've never been on a bullet train,
On say a Saturday afternoon: if I understand that page there are seven or so per hour in the afternoon (more per hour in the morning).
I will be traveling from Shinagawa (or perhaps Shinyokohama) to Osaka. At an unknown time say 1100 - 1600.
My question, can one just arrive, credit card in hand, buy a ticket at the machine or counter, and get on a train?
Or, are they typically packed and one has to buy a ticket (a few days? or?) ahead of time?
As an aside, that doesn't seem to be an honest-to-God Japan Rail web site, but it seemed to be the most convenient to display the times.