Japan, why you no have normal sized packages?!

There are a lot of supermarkets and grocery stores near our school, so you would think there shouldn't be a problem finding what you're looking for, and it isn't. BUT! It comes in too small packages!

I found potatoes, they came in a pack of four, and it was expensive too. Yea, maybe potatoes isn't really a thing of Japan but still.
Milk and yogurt that I want to eat for breakfast with musli/cereal does not come in more than 1000 ml packs and the musli is really expensive. I bought a pack that they only filled half of and it lasted for 3 portions. Bought a bigger one today just to see how long it'll last. It's way to expensive to continue to do every time.
Even for bread and ham that you put on it I haven't found any packs with more than five slices/pieces. I have just been in Japan for a little over a week though, so my complaining may be unjustified, big packs may be hiding some place unseen...

Would really like to know what most Japanese eat for breakfast, but if it's rice and miso then screw it.

For now, the only thing that I know comes in a big package is rice. Didn't see that coming, did ya?