Travel Travails & Coupons
Actually, travel coupons are few are far between in Tokyo. You can see coupons for hotel discounts if you are signed up for Groupon Japan, or Ponpare (like Groupon), but you'll have to be able to read Japanese or use the Google translate function on your browser to get a fair idea of what the coupon is about.
Jetstar offers discounts on a regular basis, but again, the announcements come in Japanese - and you have to register your email with them to get the announcements. Japanese airlines offer deals often, especially if you can book about a month ahead of time. See their offers on their websites. Most have English versions.
I've never seen a train coupon, but you can buy a Japan railpass before coming to Japan for very good deal on using JR trains. You can also get a one-day pass on Tokyo subways for around 500 yen, which is a great deal if you you are seeing a few spots around town and using the subways to get there. You can buy these in the subway stations.