Among foreign language teachers and researchers, it has been widely acknowledged that grammatical knowledge of a foreign language comprises two types of mental storage. One of the two, explicit knowledge, is quite likely linked to adjectives such as “slow” and “conscious,” whereas the other, implicit knowledge, is associated with words such as “fast” and “unconscious.” The present study challenges this conventional and popularized view, by addressing the consciousness and speed dimensions of Japanese EFL learners’ (N = 24) knowledge about tough movement. We conducted a grammaticality judgment task adopting two experimental paradigms: (a) a subjective measure of consciousness known as the meta-knowledge criterion, and (b) response time modeling. The participants judged the grammaticality of the stimuli under the two conditions, (a) control and (b) tough movement, and described their mental state during judgments (explainable vs. intuitive) trial by trial. We analyzed the dynamics among the recorded judgment responses, reaction times, and responses on the subjective measure. The results supported the hypothesis that the consciousness and speed dimensions intersect obliquely. This means that unconscious knowledge does not entail faster grammatical performance. Some pedagogical implications, particularly in light of English grammar teaching in Japan, are also discussed.