The place in Tokyo where you can attempt a foodie challenge is called Kagurazaka Hanten, and there are several giant versions of some favorite Japanese foods that you can try to eat.
When it comes to the giant food options, you have a few choices. There is a giant ramen bowl, a giant fried rice, or gyoza (there is a massive individual gyoza or a plate of 100 pieces of regular sized gyoza). They do set their food challengers some guidelines or rules to adhere to - you are given an hour to consume the massive meal, and you can't get up during the hour to use the restroom or you forfeit the challenge.
You can see the prices for the jumbo menu below. They do need some advance notice (and advance payment) for the jumbo gyoza option, as it takes some time to get it made. If you're up to the challenge and think you could get through it all, your meal is free - although I think if you managed to get through all that food you'd be full for a week! And don't worry - if you can't get through all the food during your hour, they'll pack it up for you to eat it later.
Kagurazaka Hanten is located at 1 Chome-14 Kagurazaka, Shinjuku, Tokyo 162-0825 and the closest station to the restaurant is Iidabashi. It's only a couple of minutes walk from the station.
Would you be game to give something like this a try during your trip? If so - which jumbo food option would you pick?