The purpose of this paper is to investigate the process of the acquisition of the English grammatical subject by Japanese learners of English (JLEs) within the theoretical framework of the Minimalist Program, especially the mechanism of feature-inheritance developed by Chomsky (2005, 2006) and Miyagawa (2005). In order to acquire the English-type subject, JLEs have to reset the relevant subject parameter in two steps: they first learn that the agreement feature percolates from C to T, and then, they recognize that unlike Japanese, the focus feature remains on C without percolating down to T. The result of the investigation with 673 junior high school students shows that it is relatively easy for JLEs to acquire the percolation of the agreement feature; on the other hand, they have difficulty in removing the option of the focus feature percolation. This explains why JLEs do not always succeed in resetting the subject parameter.