The Convini is short for the Convenience Store. Seriously, everyone calls it the Convini. They can't be bothered with more than three syllables apparently. So what is the convini? It's the equivalent to a 7/11 or gas station in the states. Only these are serious convini stores. They have everything you need at decent prices. Need a cold adult beverage on your way home? Coffee on your way to work? Food after work? Last ingredient for your supper? Get it here.
You can also get a new shirt incase you didn't go home the night before. A toothbrush, laundry detergent and a hot breakfast? Gotcha covered.
On my way to work I walk past 7 convinis. Some of them different, but some of them exactly the same. They offer a one stop shop for everything you need, and will provide you with everything you need for a meal. My favorite meal so far is a plate of yakisoba (which they will heat up for you), a carton of tea (which they will give you a drinking straw for), and a little box of pockys.
When you visit Tokyo get some meals at the convini. Try them out, don't be scared. It's a great way to use your coins that you'll inevitably stock pile.
The cashier puts all of the things I buy neatly into a bag, with the necessary utensils and a moist cloth to clean your hands. They twist the handles and away you go! A full meal for around $6. If you time it right, you can get marked down meals because they are made fresh every day. Fresh? At a convini? You betcha! And let me tell you--the food is better than any other $6 meals I have found in Tokyo, and you get a drink!