It is well known that a plural marker is optional in languages that allow bare nouns, unlike English that does not allow bare nouns. This is so as a bare noun can denote either a singular or a plural meaning. However, in recent studies, it has been identified that even in a bare noun language such as Persian or Korean a plural marker is obligatory to indicate a plural meaning. The requirement of plural marker in these languages is identified to be only possible in an anaphoric context. This paper addresses an issue of why such a context in a bare noun language requires a plural marker. In particular, this paper focuses on the syntax of plural and anaphoric context that make possible the obligatory presence of plural. By building on the previous approaches on this issue, this paper proposes that a plural instantiates the Num(ber) head with a binary number feature such as [±plural]. Via Agree (Chomsky 1998), the feature on the Num head values an uninterpretable number feature on the D head that is the locus of definiteness. This paper shows that Korean allows an obligatory plural marking similar to English, but only in a restricted context, i.e., anaphoric context. Moreover, this paper identified that the strict presence of plural marking in Korean is cross-linguistic phenomenon found in other bare noun languages, which has not been paid much attention in the literature.