I just went to Odaiba a few days ago.
And I found this restaurant called AQUA Dining ATU.

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For your information, during lunch time they have a Lunch Buffet Which cost you only for 1350yen (sekitar 135rb rupiah), for primary school student 850 ( sekitar 85rb rupiah), and for 2-5 years old only for 500yen (sekitar 50rb rupiah). 
And when I tried to find other restaurant to eat, I can tell you that this is the cheapest restaurant in AQUA City and this place has the best view of -> the rainbow bridge, tokyo tower, sea, and many others!
How awesome is that?!

P.S During the night the restaurant will turn into bar.

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They have salads with different kinds of toppings, pudding, fruits...

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Rice, Tofu, Pasta, Karage and other Japanese and Western food.

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And the surprising thing is they have an aquarium with a shark inside it -__- HAHA

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Here is the food that me and my friend took.
And a tip for you, maybe if you are indonesian, you will mix everything in one plate if you are having a buffet, “like me” HAHA But, Japanese people seperates everything.
For example if they want to take pasta, they will put the Pasta/Western food in one plate, Japanese food in one plate, Salad in one plate, and Fruits in one plate → Not like me.. HAHA

But yes do separate your food. :)

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They have soup too and the best soup is the corn soup..

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Not forgetting Gyoza!
Bread Miso Soup and others...

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And you can choose your seats either outside(Smoking Area) or inside(Non Smoking Area).

And the best part of it, the restaurant have a big balcony and you can take a 360 degrees of Odaiba!

Well if you go to Odaiba don’t forget to eat buffet here at AQUA Dining ATU! :)

Map:

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