It's interesting to see McDonald's Japan offering a "Big Breakfast" (available until 10:30 a.m. where available) because my impression of the sorts of "traditional" Japanese breakfast that I keep reading about on the internet but rarely heard anyone eat is that they are actually pretty "big". If you haven't read about it, we Western folks are told that Japanese people eat rice, fish, and miso soup for breakfat. To us, that's dinner, but there was a time when that was the common deal in Japan. Most of my students told me that ate "bread" (i.e., toast or a bun of some sort) with tea or coffee and sometimes some sort of cup-a-soup (like corn potage).
So, the idea that the breakfast on offer at McDonald's are "big" compared to what we're told Japanese eat is a strange one. It's only big compared to what my former students and I tended to eat because I'm with them in this regard - coffee and some sort of baked item is the norm.
Getting to the point though, I think it's interesting to note what passes for "big" in Japanese marketing. There are actually two versions. The one I'd term "big" is scrambled egg product, a sausage patty, an English muffin with available packets of jam, and a hash brown. To a great extent, this appears to be a deconstructed Egg McMuffin plus a hash brown. The "bigger" version (marketed as "deluxe" in Japan) also includes a couple of pancakes.
The deluxe will provide you with 934 calories of power to start your day being shoved on crowded trains, hiking to the office, and pushing papers around and nodding and saying "hai" ("yes") to everything the boss suggests. This is quite a wallop considering that Denny's grand slam (original) is a punier 770 calories for 3 eggs with cheese, two bits of bacon or sausage, and your choice of hash browns, bread, or grits.