How much Yen for a month stay in Japan?

I will be in Japan for about a month (hopefully), maybe a bit longer. I am going to be staying with a host family so food and accommodation are paid for. So, really I will only need enough to pay for airfare and any transport to and from the place I am staying.
I am planning on having around 300,000 yen. Could anyone tell me if this is a reasonable amount of money?

If that includes airfare, you might want to take a bit more if you want to see the sights.

where is your host family located ?

I am staying with a family outside of Kyoto. I was planning on flying into Tokyo, so I can't imagine it being too expensive to get from Tokyo to Kyoto.

Another important question; "from" where are you flying to Japan, if that money needs to include airfare? :)

I will be flying from Edinburgh Scotland.

Airfare-wise, I would recommend going through Opodo/cheapflights.co.uk since you can get some real bargains for flights from Edinburgh.

Expenses-wise, it really does depend on how much you want to see, as well as if you want to buy a lot of souvenirs and do things like dress up as a Geisha, which is available.

If you plan to travel around all parts of the country, getting a JR pass before you go is probably the best bet, since it means you can hop on and off JR trains from Hokkaido all the way down to Nagasaki. Single/return ticket prices for one trip from Tokyo to Osaka can cost almost as much as a week-long JR pass, which would let you do the same journey multiple times at no extra cost.