

Dave,
I have traveled a lot around around Japan doing a lot of hitchhiking, biking, and camping, sometimes for weeks at a stretch. My experience also includes roughing it on 4 other continents and a pilgrimage known as the Camino de Santiago in Spain. Anyhow I figured I could offer some advice about the extreme cost saving approach to traveling in Japan. When I travel, once on the road, my expenses come to basically food and nothing else.
The most important thing is how you travel. I always go light. I take the same amount of clothes. 3 T-shirts, 3 pairs of shorts or pants, 3 pairs of socks, 3 pairs of underwear, and a gore tex windbreaker. Aside from the windbreaker all of these articles are made of acrylic, nylon or some other similar synthetic fiber. The reason being that this type of clothing is light and will dry quickly when wet or sweaty. Second, the clothes I have is all black except for the t-shirts and windbreaker. This is so that they do not become noticeably dirty even when they are filthy. As for the shirts and windbreaker, I always opt for something red as to improve my standing out. This is to avoid being run over. In the event that travel is done in cold weather some additional wool clothing can be thrown on the list. Everything I put in to ziplock bags within my pack. The stuff I am not likely to pull out often I'll double bag with a trash bag.
The two sets of clothes I alternate between while traveling. I will try to wash them whenever I can, sometimes even more than once a day. In summer or warm days the clothes can be washed, wrung out and put on straight afterwards. In colder temperatures they will need to be hung from the pack while walking. The washing can be done at any public bathroom in the sink, or where there is access to clean running water. I never use detergent. I only carry unscented glycerin soap. It can be used as a detergent, body soap, and lather for shaving. It is also safe for the environment and does leave much residue. The washing I do in the bathrooms at parks, drinking fountains or where ever there is a public hose or faucet. A rinse off will do most of the time. If it cant be done nude I usually do it with my clothes on, only removing the expendable articles.
The last set of clothing I keep as my clean clothes. This is to never be worn while sweating, nor after sweating unless having properly bathed first. It is for when you might stay at a proper lodging, be invited to stay the night somewhere, or otherwise want to be presentable.
For camping I carry a small tent, the smallest you would possibly need. A gore tex bivy tent works best. They are light, easy to set up, low lying and hardly visible. I then carry a roll up mat and a compact lightweight sleeping bag. In summer I will forgo the sleeping bag.
The best place to camp out in Japan I find is at shrines. They are everywhere, from the big cities to the smallest towns. They are also marked on maps with the "manji" symbol. You know the symbol that looks like a reverse swastika. Simply go to one after dark, slip in and set up camp in a corner somewhere. Since they are public places you cant be accused of trespassing. At worst you will be asked to leave. On the rare occasion that has happened to me I have always been able to talk my way out the situation by saying I will leave first thing in the morning. Parks are also okay too. School grounds I have done but have been kicked off of as well. Along rivers on concourses work. There is usually a level area with grass. If worse comes to worst you could politely ask to camp out on someone's property after first having asking them where the closest of the above mentioned areas is.
The biggest problem with camping is rain. When raining it makes finding a spot even harder. Since in Japan rain can strike at anytime I try my best to find a covered area to set up and camp under. This is because I dont want to get wet while sleeping. Unfortunately, through continued use even the most expensive tents will lose their waterproofness. The problem can be torn seams, but usually it's small holes that get poked through the bottom by pine needles, pebbles or what not. If they arent that large you can close them up with a sealant. But you wont know when to use it until you have a problem. A mat helps to prevent these holes by creating a buffer between your hard body and the ground. Sleeping over soft earth that you have cleared beforehand will also lengthen the durability of a tent. But to avoid any possibility of getting wet set up your tent under roofs, overhangs, bridges or at least on slightly unlevel ground where water will not collect.
For food, it is best to go to supermarkets. They are cheaper than convenient stores and have a wider selection. But if convenient stores are the only thing around you can still get some food at a low price. I usually go for the onigiri riceballs and a type of bread. Each goes for about 100 yen a piece. Nikuman or Pizzaman meat buns are also okay. If you forgo the drink by only having tapwater, one meal consists of four items. Three I eat on the spot, one I save for the road. That is 400 yen a meal. If you think it is going to be a while until the next store youll of course take more with you. It should all come to less than 1,500 yen a day for food even when particularly hungry.
Some people may argue that it is better to cook while you go along, but I disagree. Rice and veggie meals are about the only thing you can save money on. For the most part in Japan groceries are expensive unless you cook in bulk. It may work if you are in a group, but otherwise no way are you going to want to carry around all that food throughout the day. You will also need to have the cooking gear. Thats a lot of additional weight and loss of space. Unless you are in the boonies and it is absolutely necessary because of a lack of stores I dont see the point. You would still be hard pressed to get by on under 1,500 yen a day. I know because I live in Japan and always cook at home.
In Japan you are never far away from civilization. If you find you need something that you may have forgot to packed, chances are you can buy it along the way. Travel light. And get the Super Mapple Road Map for the region you are in. It is a little big but worth the space. It shows the locations of convenient stores, gas stations, supermarkets, shrines, temples, schools, parks, and lists distances. A one time investment of 3,000 yen is all it takes. If thats pushing your budget you can flip through one at any convenient store and make 10 yen photocopies of the important pages. Super Mapple Road Maps have been indespensable on my many bike trips throughout the country. There is one for !!all of Shikoku that you can buy after arriving.
I know cheap. I once hitchhiked for two weeks from Tokyo to Niigata, along the coast to Toyama, south to Kyoto, around through Nagoya and back to Tokyo. I spent only a little over 30,000 yen on the road, half of which went towards paying to go inside temples and castles. At the time I was seriously that broke and could not afford better. However, on my other trips I usually dont rough it so badly. What I eat, what I pay to get in to, and how I get around makes the biggest price differences.
Anyhow, for an adult male American traveling around on a minimal budget, that is how I do it. I now speak Japanese well, but before when I couldnt I still managed. Japan is safe and a very convenient place. The people are also friendly and helpful. If you mean well and try your best the locals will be supportive of your traveling ways. At least that is how it has been for me.
Phil in Minokamo, Gifu, Japan