This study investigated factors responsible for the developmental discontinuity of children's language processing in Japanese. We conducted an experiment using cross-modal linguistic stimuli (prosody & orthography) to see whether children’s orthographic knowledge affects their rendaku strategy or not. Our results showed that orthographic cues affected literate children’s rendaku processing. They were aware the correspondence between types of orthography and word categories in Japanese. Children define the rendaku category and redefine it, resulting in the qualitative change in children’s rendaku strategies.