Regarding mass nouns:
Japanese requires classifiers in order to count nouns, but there are other ways to confirm that this does not necessarily mean that all basic nouns are mass nouns, even if they are not directly countable.
The word darake "full of; covered with" (which is more of a suffix since it can't stand on its own) is used directly on nouns with no classifiers. When combined with mizu "water" → mizu-darake means "covered with water; water everywhere". But combined with inu "dog" → inu-darake means "full of dogs; dogs everywhere"; it does not mean dog meat and entrails have been smeared all over the walls (though if that somehow actually happened, I suppose you could use this term for it as well, but it would sound pretty crass "There's dog everywhere!"). From this we can tell that some nouns are not mass nouns.
There is also a distinction like English, ikura "how much" vs. ikutsu "how many", though these are more restricted in use since the normal way to ask is "what" plus the classifier, so this also illustrates that a mass/non-mass distinction exists despite the existence of classifiers that obscure it.
If you're new to these arts, this is the place to ask "stupid" questions and get directions!