If you travel between Tokyo and Osaka, taking the bullet train called Shinkansen is the way to go because it takes only two and a half hours. But it’s pretty expensive. The round trip fare is around 250 dollars for each person. If you don’t want to spend that money, taking a bus won’t hurt. The fare for round trip is approximately 100 dollars. However, it takes about 7 or 8 hours. There is also overnight buses which you can travel while sleeping, but I don’t recommend it especially for people with large body frame or not so young because the seats are not good enough to sleep. That being said, I used to use it when I was young though.