If you’re looking for more economical ways to travel domestically within Japan, several companies offer great values with their long distance express buses that run on Japan’s expressways between most major cities and to many main tourist destinations. One of them is Willer Express. While it may take a bit longer to reach your destination, you’ll reach it in comfort, safety, and knowing that you’ve saved a pretty penny! Overnight bus service means also that you can save on accommodations!
The Japan Bus Pass that Willer offers is available in 3-Day or 5-Day sets of tickets and each set is valid for two months from date of purchase. These passes let you design your own trip, and the tickets don’t have to be used on consecutive days, giving you the flexibility to enjoy your travels.
For more information on the Willer Express Bus, please visit here.
For more information about traveling Japan by bus, visit here.
The overnight bus should really be your last possible option. I've done it several times. Everyone reclines of course, and the seats are so close that your nose almost touches the back of the seat in front of you. It's fairly comfortable though, and the bus also has a little lounge area. As long as you're the type who can 'sleep anywhere' it's not bad, and I suppose if you weren't then you would never travel in any kind of bus.