Convenience stores in Japan are totally awesome, and very different from back home in North America. You can find 7-11 and Lawson everywhere in Tokyo, and we were lucky to have a 7-11 right under our hotel (near the Tochomae station on the Oedo line).
What we learned about Japanese konbini? It has good coffee, served from vending machines for about $1. And, if you like your coffee cold, there are tons of canned cold coffee options (I liked Boss latte’s myself).
We had a 7-11 breakfast most mornings, as a way to keep that meal cheap and cheerful. There are options like yogurt and pastries, but I usually ended up having a sandwich (very fresh, with the crusts cut off – I liked the creamy egg salad the best) and/or a rice ongiri ball, and Dave usually went for a packaged meal of chicken and rice that was heated up in the microwave. We also chose noodles some mornings, because it was easy to heat up water in our kettle in the hotel room.
Of course, Konbini also have great snacks (Dave loved the Karaage fried chicken) and beer and wine, so we went to the 7-11 often at the end of a day trip to stock up.
Konbini are a great way to keep costs down on a trip to Japan, while still sampling great tasting Japanese food!