Day buses from Tokyo to Osaka

I would be spending 15 days in Japan traveling from Tokyo to Osaka. In between my traveling, I would like to take the day bus from Tokyo to Osaka. Aside from the Willer Bus, does anyone know of any bus company in Japan that travels in the daytime from Tokyo to Osaka? I prefer websites with English characters. My budget for this bus travel is between 5000Y to 6000Y at most. Any feedback would be highly appreciated. Thanks

Willer is probably the least expensive bus option; however, the following link will provide you with other bus options:

http://www.japan-guide.com/e/e2366.html

5000 to 6000 JPY could also get you a low-cost flight at Peach or Jetstar, depending on dates.

Any other bus options with English sub-characters? Any other non-bus options?

Willer allows online booking 3 months in advance. I am going to book immediately once they allow booking on the said date. There are 3 time slots of day buses going to Osaka. With that said, what is my probability of getting a seat? Can I say 100%?

I agree with firas, I just looked up on peach and the price is rather cheap, my next trip to japan I will try out peach for Tokyo to Osaka and from Osaka to korea.

price from Tokyo to Osaka prices range from less than 5000yen and up.