There are conflicting hypotheses for the causes of Dyslexia in reading and writing difficulties, such as the phonological deficit hypothesis, double deficit hypothesis, magnocellular deficits hypothesis etc. The cause of the difficulties may vary between individuals. Moreover, most of these hypotheses consider only a single disability, despite the fact that factors related to reading and writing may affect the difficulty in various ways. We conducted this study to identify individual differences in the effect of Dyslexia. The participants were 12 Japanese children who were diagnosed with learning disabilities or suspected to be learning disabled. In this study, we considered how phonological awareness, visual perception, and phonological processing are related to reading and writing abilities in the Japanese language. In addition, we checked “handwriting ability.” This study shows that reading and writing difficulties are caused by a variety of factors and that there are individual differences in the difficulties.