The first thing I would say is if you are going over without much money, you need to have a backup plan. What if you miss your plane? What if your keycard won't work? Japan is a cash society so you'll need to carry some cash.
- Carry a Visa Card that you can withdraw cash from (last time I took a Mastercard, and 7 11 stopped taking this making getting cash very difficult)
- Ensure Relatives can top up your account if required
- Take travel insurance (including health - not negotiable)
I'd say go for a shorter time to have a better time.
When my credit card didn't work, I had to forgo the 5 star hotel I had booked and stay here:
ACE INN Shinjuku-We are ACE INN, BACKPACKER'S HOTEL in Tokyo.
There was a share shower, and I did stay in the "luxury" section. Even though there was about 40 beds or something - only three were full on a whole floor, making it similar to having my room.
There was a share shower that cost a dollar or thereabouts.
Really - even though I am a 5 star person, it was definitely okay. I'd say you can pay $50 per night and stay at some okay places. Have a look on Trip Advisor (
Ace Inn Shinjuku (Shinjuku, Japan) - Capsule Hotel Reviews - TripAdvisor. I really liked the Capsule Hotel aspect of Ace Inn Shinjuku - though some say it's overpriced, and the lower floors can be noisy, I found it to be a welcome home sweet home.
I also picked up about 5 unlocked wireless internet connections from the comfort of my capsule! There was a locker for possessions.
As for drinking and eating - well for some alcohol as a nightly relaxant, you can always start with the vending machines (just don't get feral - you're representing your country
)
Food - well, really the first time, I didn't know how to order in Japanese, so I lived on 7 11 food, which can be healthy. Salads, tofu rolls (and then your sweet buns for just a few bucks each)
I'm talking Australian dollars / US dollars here (approximating $1 to be about 100 Yen)
I'd say carefully plan - because there might be places where your dollar would go further. If there's two of you, then perhaps you'd get better value from a hotel in a business district like Otemachi.
Around Ueno is meant to be some cheap hotels - but I found that they were overpriced and the one I stayed in was sooo dingy (despite okay reviews). Just not worth it.
Don't let a train trip scare you off. Five stops from Tokyo is nothing, and you need to know how to use the trains anyways.