Japan is a country of "attention to detail" and this applies to the food also. When we cook, we sometimes cut out vegetables using cookie cutter rather than just slicing it and further out, make them 3D with more cuts and slices. It may sound like too much work but Japanese people (not every !) are happy to spend some extra time for better presentation. When you eat Japanese food, have some time to enjoy it with your eyes before you enjoy it with your mouth !
Christmas is basically just an excuse to party for Japanese people but we are serious about Christmas cake. Christmas cakes are available everywhere and even those who don't usually eat cake get one.. Local cake shops not to mention, chain cake shops, food floor of department stores, convenience stores, supermarkets, grocery stores...everywhere. Convenience stores sometime team up with famous patisserie, matcha brand, chocolatier to make exclusive cakes and these are actually good ! If you are in Japan around Christmas, try one !
We do but only maki (rolls), chirashi (scattered), inari (bean bag) and temari (balls) and never nigiri. Nigiri seems so simple and easy to make but it's full of professional techniques. Fish has to be sliced properly, rice has to be held strong enough to stay together but weak enough to easily fall apart in your mouth. So let's leave it to professional and stick to maki at home.
Technical speaking, no it's not ok. It's considered better to keep the soy sauce as clear as possible for better look. And also, there are some seafoods that go well with other condiments such as grated ginger and if you have wasabi dissolved in soy sauce, it will kill the flavor of the other condiments and it will all taste like wasabi. But there are some Japanese people who do dissolve wasabi and I think it's ok to do so if it taste better for you that way !
If you like Japanese curry, this one is definitely worth trying in Japan. Japanese curry wrapped in bread dough, breaded and deep fried. Available at bakeries or even at convenience stores !
Do Japanese people eat sushi everyday ? No we don't. A research shows 25% eat sushi 2~3 times a month, 30% once a month, 30% less than that and only 5% eat more than once a week.
Sushi is probably still the most popular Japanese food in your country but it's just one of many in Japan ! .
When you are traveling to Japan, you may think "I'm gonna eat as much sushi and other delicious Japanese food as possible and there is absolutely no way that I eat fast food !". Are you sure about that ? Many fast food restaurant chain do Japanized menu and this one is Japanese chicken katsu burger from KFC. So one more time. Are you really sure about that ?
You can find many western foods that were Japanized in Japan. Teriyaki pizza, spaghetti with soy sauce, chicken Katsu burger, Japanese fried chicken called Karaage, matcha doughnut, you name it. And popcorn didn't get away with the japanization. You can find butter and soy sauce flavored popcorn at movie theaters in Japan. It smells so good and you feel like getting one even if you weren't planning to do so !