In successful communication, it is critical to have the ability to identify what a speaker is referring to from previously mentioned information. This ability requires the identification of the topic initially introduced by lexical forms and its continuity in discourse expressed by anaphora such as null and pronominal forms in the subsequent sentences. While Japanese-speaking children are frequently provided with pronominal and null forms, especially the null form, in reference to previously mentioned topics, it remains unclear from what age they understand the anaphoric use of such referential forms. The current study investigated the age at which Japanese-speaking children are able to identify the presence of topic chains connecting null and pronoun anaphora to the topic referred to by a lexical form in the preceding sentence. We tested children's comprehension of null and pronominal object sentences using an intermodal preferential-looking paradigm. The results demonstrated that the Japanese-speaking children aged 2;7 and 3;2 as a group looked at the target animation reliably longer after hearing the test sentences than before or during the test sentences. This finding provides evidence that Japanese-speaking children's ability to track topic chains and understand anaphora in the discourse develop by 2;7 years of age. However, unlike the 3;2-year-old group, the 2;7-year-old group showed weaker performance in interpreting pronominal object sentences, suggesting a possibility that young children find the interpretation of null anaphora easier than that of pronoun anaphora.