This diet is nothing like what Japanese people eat; after living in Japan myself twice, I have yet to see any of these "meals" in any traditional restaurant, nor have I seen this "famous" diet plan mentioned by doctors or on TV.
If you want a Japanese diet plan, here you go:
Rice and miso soup for breakfast. It's the basis of most any Japanese meal, and with tofu and wakame in the
miso, you get a decent start to the day. Natto is often eaten with rice in the morning.
Lunch and dinner will both have rice, some sort of meat (fish, thinly sliced pork, hamburg, etc) and vegetables. Boiled vegetables (nimono) and pickled vegetables (tsukemono) are very common side dishes in any given traditional meal. Miso is also a common side dish with lunch and dinner. If you get salad in Japan, it will likely be shredded cabbage with sesame dressing, or some sort of seaweed-based small salad.
Portions are probably the main difference, though. Yes, Japanese food is healthier, but the portions are also perfect for one meal. None of those huge restaurant portions you get in the States that could feed a family of four.