This chapter presents descriptive generalizations of plural marking in Japanese with the morpheme -tati and proposes an account for its distributional and interpretive properties that are puzzling in many ways. The semantic peculiarities of -tati plurals, such as their tendency to be definite and the lack of generic and kind interpretations, result from the use of -tati as an associative plural marker. When -tati attaches to an individual-denoting expression, it denotes a plurality that consists of the referent of the expression and entities associated with. It is argued that -tati maintains this associative meaning even when it combines with a common noun. The extended notion of associativity allows X-tati, where X is a common noun, to include non-Xs in its denotation as long as such entities are closely associated with X, yielding similative plurals. This potential heterogeneity can solve most, if not all, of the puzzles posed by -tati plurals.