Supermarket sushi is either the culmination or end of civilization. I can't tell.
Arpico now has a sushi stand in the middle of their Hyde Park outlet and the results are well, not bad. Colombo definitely has better sushi options, but nothing this convenient.
Supermarkets in general are a bit of a tease. You're surrounded by food, but you can't eat it. Iwata breaks that rule by letting you order sushi (or fruit juice) right next to the vegetable aisle.
There is seating but the place seems mostly geared towards takeaway. Everything comes in takeaway boxes and they bag it up unless you ask. We ate in, which is fine, but there's nothing much to the ambience here. You are just eating sushi in the middle of a bright supermarket.
Good sushi can make you close your eyes and have a little brain orgasm. This doesn't do that. It has all the ingredients of sushi and is a good enough carrier for large quantities of soy sauce so basically, it's fine as a snack.
It's not crazy cheap though. We got three tekkamaki (tuna) and two salmon rolls, which came to Rs. 750. You can get a full, resplendent bento box delivered from Naniyori for not much more, and that's much more satisfying.
They've got vegetarian sushi too, as pictured above.
Overall, the food is OK, but the salmon tasted not crisply fresh (the roll tasted mostly of butter, somehow) and it seemed like there wasn't any particular attention paid to the balance of the rice or any other ingredients.
Iwata's printed menu actually only lists juice, which we haven't tried so, er, mention that in the comments if you have.
Service etc is fine, there really isn't that much to review here. This is basically another stall inside the supermarket which happens to have prepared food you can eat right now. Neither the food nor the ambience are really the point here.
The marriage of convenience between sushi and a supermarket is everything here. If you are in a supermarket and hungry this option won't kill you and it's kinda fun for novelty's sake. Iwata is not something to go out of your way for, but neither is it something to avoid.