Pizza in Japan is served with Tabasco sauce (or packets of “hot green sauce,” like this one from Pizza Hut). This is unfortunate, as the crust of Japanese pizza is typically already saturated with oil. Also, crushed red pepper (my pizza condiment of choice) is unavailable here.
“Mottainai” in this context basically means “don’t be wasteful,” and there are directions on the outside of the cardboard box so you can fold it down to a manageable size to put out with your paper recycling.
Oh, and pizza is phenomenally expensive here. Medium pizzas start at about $12, and a large will set you back about $30.