Reading in a second language (L2) is a complex processing that involves an interaction between L2 and the native language (L1). To investigate the fundamental mechanisms, this study used functional magnetic resonance imaging (fMRI) to visualize Japanese-Chinese bilinguals' brain activity in semantic processing of Chinese and Japanese characters. Using fMRI, much knowledge has been gained in understanding how the brain is activated during controlled experiments of language tasks in alphabetic subjects and in logographic language subjects. In this study, we used fMRI to investigate brain activations in processing Japanese semantic and font size by visual judgment tasks in fifteen Japanese subjects. Different activation patterns were observed between semantic and font size judgment processing. We conclude that constellation of neural substrates was different for semantic processing.