Syntactic bootstrapping facilitates children's initial learning of verb meanings based on syntactic information. A challenging case is the argument-drop languages, where the number of argument NPs is not a reliable cue for distinguishing between transitive and intransitive verbs. Despite this fact, the availability of syntactic bootstrapping in Japanese (Matsuo et al., 2012) implies that case-marking particles play a role in the identification of a verb's transitivity. This study investigates whether Japanese-speaking 2-year-olds infer the meaning of novel verbs using case-marking cues as well as typical transitive/intransitive frames. The results of the intermodal preferential looking paradigm showed that they made transitive-causative association, even when only a direct object marked with the accusative case was provided. This indicates that children can utilize case markers as cues to a verb's transitivity. We suggest that all these discoveries provide support for the availability of syntactic bootstrapping in Japanese and its universality in language acquisition.