Originally Posted by
nishimark
There are also overnight buses available. They're cheaper than the train by at least half, plus you don't have to pay for a hotel that night. Also, you don't spend half a day on travel. They are made to sleep on (reclining seats), but not sure how well you might sleep in a reclining bus seat as compared to a bed.
http://willerexpress.com/en/
Unless they've changed the buses in recent years, people who are large (either horizontally or vertically) would find the buses tough going.
I enthusiastically suggest the train. You got central city to central city in about three hours in a comfortable setting, and you get to see some of what the country looks like outside the major cities. If it's between, say, December and March, when the air is clear and dry, you may see Mount Fuji out of the north side of the train.