Itinerary and general information

Hello all,

I apologize for the bad english in advance.

Im thinking about a spontaneous trip to Japan for between 3 weeks and a month.

I spent the last day trying to read as much as I can about the country and even bought the Lonely Planet book but their is too much information for me to consume in such short time.

I'm a backpacker currently in Bangkok and plan to fly from here to Tokyo maybe next week or the week after.
My flight back will also be from Tokyo so obviously i need to do sort of a round-trip.

Since I don't have too much money too spend, I spent most of my time reading the budget part of this website.

My general itinerary is to start in Tokyo for a couple of days, continue westward maybe up to Fukoka for the sumo tournament and back to Tokyo for my flight back.

Seems reasonable to pick the Willer bus pass for the trip from Tokyo westward to Hakata. I guess I'll need a 5+3 bus passes to complete the journey one way, and maybe take a bullet train back to Tokyo to try it once.

I'm a relaxed traveler and don't like running between places so I think I need to pick maybe the highlights on the road. I enjoy big cities very much but would also like to feel the vibes of the country side and the spiritual temples nontheless.

Could anyone recommend an itinerary that is reasonable? I checked the website's itineraries but they seem rushed a little bit.
Any general information and tips you can think of would be great to try an eliminate first-timers mistakes in Japan.

Thanks so much!

i kept on reading and this is what im thinking of doing.. it looks like everything is set by the JR rail pass so i guess i'll have to shorten the trip a little and buy it.

Day 1: Arrive Tokyo
Day 2-3: Tokyo
Day 4: day trip to Nikko
Day 5: day trip to Kamakura
Day 6-7: Mt. Fuji area (lakes)
Day 8: Takayama (through Nagoya with only changing JR's)
Day 9-10: Japan Alps
Day 11: Kamazawa
Day 12-15: Kyoto + Nara
Day 16: Koya San
Day 17-18: Osaka
Day 19-20: Hiroshima and back to Tokyo
Day 21: Tokyo (shopping) and home!

I hoped to do this route without rushing but it is just too expensive.. what do you think about the itinerary? the JR pass is needed right?

Thanks all!