One of the remarkable differences between finite relative clauses and infinitive relative clauses lies in the presence of overt relative pronouns. Unlike finite relative clauses, infinitive relative clauses do not permit overt relative pronouns except the case in which prepositions are pied-piped. This paper proposes that the distribution of overt relative pronouns can be captured by the constraint that both the relative pronoun and the modifying marker to must be adjacent to its antecedent. If there is an overt relative pronoun, to cannot be adjacent to the antecedent, which results in ungrammaticality. This paper extends this Adjacency approach to the phenomenon that there is no overt relative pronoun in Korean. I argue that if there were an overt relative pronoun in Korean, no grammatical sentence could be generated, for it could not be adjacent to the antecedent or would prevent the modifying marker (n)un from being adjacent to the antecedent.