This study presents a computer simulation model of reading in Japanese syllabic kana and morphographic kanji. The model was based on the simulation model developed by Harm and Seidenberg for reading in English. The purpose of building the current model was to verify the validity of the hypothesis of granularity and transparency (HGT) postulated by Wydell and Butterworth, focusing on the granularity dimension. The HGT was developed in order to explain the behavioral dissociation between excellent reading skills in Japanese and poor reading skills in English of an English-Japanese bilingual individual as well as the relatively low incidence of developmental dyslexia in Japan. The current model was successful in simulating the granularity dimension of the HGT. The study also identified several limitations, which need to be addressed in future research.