It has been argued that languages differ in the extent to which they allow plural forms of nouns according to the Animacy Hierarchy. Japanese distinguishes between animate and inanimate nouns; the latter are less likely to receive plural markers (e.g., ?hon‑tachi), unlike English. This L1-L2 difference might cause difficulty in acquiring the plural morpheme. The present study thus investigates the influence of animacy on the processing of the English plural morpheme in online sentence processing. In this study, 34 Japanese university students engaged in a moving window version of a self-paced reading task, during which they also judged whether the number of words presented was one or two when prompted. If animacy matters, Japanese EFL learners might not show an interference effect of this second task for inanimate nouns. However, as no such effect was found, the prediction based on the animacy hierarchy was not confirmed.