This paper focuses on the semantic analysis of noun phrases in Japanese with respect to kind reference in generic sentences. Chierchia(1998) argues that bare plurals and mass nouns in Germanic languages can denote kinds (individual concepts) so that they occur in argument positions, whereas nouns in Romance languages always call for determiners(e.g.articles) since they stand for predicates, i.e. sets of objects. Chierchia argues further that all Japanese nouns refer to kinds because they behave like mass nouns and function as arguments without determiners. Contrary to this view (also Krifka 1995) we argue that Japanese has distinction between singular count nouns and mass ones. In Japanese most quantifiers can be combined only to count nouns, but not to mass ones. There is also a plural morpheme "tachi" that can attach to count nouns with animate feature and denotes plural objects. We propose then that Japanese bare nouns are predicates, but can function as arguments by virtue of free applications of a type-shifting operation. In our analysis mass nouns correspond to sets of singular and plural objects. The kind reference of a mass term is derived by the 'down'-operator that changes a property type denotation to one of a kind type. Count nouns are shifted to mass-like collective nouns by the 'massification'(=group forming) operator and then denote a kind denotation by the application of the iota-operator. This explains why it is sometimes difficult to get a plural meaning with a bare count noun: Massification as a pluralization operation can apply to a count NP only if its collective reading is possible.