Cheapest transportation for my itinerary

Hi Everyone,
I'm Coming to Japan this Sunday for three months, this why my question is very urgent!
i intend to circle all japan except Hokaido (Travel all Honshu,Kyushu,Shikoku)
but i can't decide if it's better to buy three rail passes (each for 21 days) or to use the local passes, night busses etc.
i'm travleing budget style, but i will move a lot.i want the cheaper option.
(21 days pass costs 57000yen)
so what's better for me, and why?

An aspect that you can't forget about when it comes to night buses is that you'll usually also save money sleeping on the bus rather than in a hotel. Not sure if you've already made reservations for accommodations yet.

If you really want to save money, I'd go for the night bus option. Even when you say that you'll move a lot, unless you're going to be taking the Shinkansen and various limited express trains throughout, I don't think you'll get the full value of your pass.

You won't really be using the pass to its full extent when traveling within a region. If the only long-distance travel is between region to region, you can easily take a bus.

i just got back from a 5 week trip and i was just traveling around the honshu island but i went around and took the night bus. if you're spending quite some time in certain cities than it is probably a lot cheaper to take the bus. it is only worth the value for the rail pass if it is a short period of stay and you plan to do an immense amount of travel. you may find that in certain areas like osaka, you can stay in osaka or kyoto and make day trips out and around to places such as nara n kobe for a very cheap price.

i suggest willer express for night buses. they have a span of buses to the major cities around japan and there is also online booking in english. you just need to know where you're going and internet..then you're set. a trip from tokyo to osaka for willer express is roughly 3500yen one way compared to the roughly 13000yen on the bullet train. i spent a total about 31000yen for overnight buses during my 5 weeks which is only a mere fraction of the price you will be paying if you get 3 rail passes and i went to various cities. you can also be more flexible if you take a night bus

I would also suggest the three seater seats/bus as it would be more convenient and comfortable esp if you are travelling alone. JR pass - too expensive and awaste of money, Besides night buses - you could even take the local train and break up your journey and stop by for one or two days at other places.