I travelled quite a bit and found that Minshukus can also be a cheap alternative (specially in smaller citys) to Youth hostels. I did alot of hitchhiking wich also saved me money and i ate cheap every day.
I ended up spending 7400yen a day while travelling and around 4500yen a day while staying in a Guesthouse in Tokyo.
So, we are talking about around 260 000yen budget wich would keep me travelling for around 1 and a half month and i could probably live for 2 month in one city. I think it should be possible to cut my budget down, but then your trip will end up not beeing enjoyable. Sleeping in internetcafes, eating conbini food everday, only travelling by night bus and not spending any money on going out and i´d say you can do around 6000yen a day.
My one month spending for travelling in Hokkaido (Sapporo, Furano, Biei, Asahidake, Wakkanai, Rebun iland, Monbetsu, abashiri, Shiretoko, kawayu, Akan kohan, Kushiro, Obihiro, Erimo, noboribetsu, Murano, Toyako Onsen, Otaru and back to Sapporo) looks like this:
Accomodation: 110 000 (sleeping in Minshukus, capsule hotels and youth hostels, spending 1 night in a 9000yen Hotel)
Food: 45400 (eating mostly ramen, fast food, convinience store food, sometimes something nice)
Entryfees: 1500
Transportation: 32400 (using local trains, buses and hitchhiking )
Other things: 37400 (wasted most of it on games, bought a prepaid card for my mobile phone, paid for my new driving license,...)
Oh, i dont smoke and hardly drink alkohol, so if you´d like to do that, ad it up on top (or change it with my gaming cost
