When I was in college, Greyhound was a necessary evil. Generally, I just sucked it up and suffered through the three hour trip from Maine to Boston (where the girls were), but it was pretty miserable. Japan, though, has managed to turn bus travel into what looks like first-class air travel, with extreme luxury seat modules that they call cocoons.
Willer Express, which runs from Osaka to Tokyo, only seats twelve people. But each of those people gets their own personal relaxation pod, complete with a seat that reclines 140 degrees, a personal entertainment system, free WiFi, dedicated power outlets, and high partitions to separate you from your annoying fellow passengers.
Of course, there's no getting around the fact that unlike an airplane, buses can get stuck in traffic, but on the other hand, you don't have to subject yourself to a security screening either, so it might all even out in the end. It'll cost you about $130 for a one way, six or seven hour trip (so, about the same as a long distance train ride in the U.S.), and for what it's worth, this is both cheaper and more luxurious than taking a bullet train, even if the train will get you there in just over two hours.