Research on the L2 Motivational Self System has drawn considerable attention in Second Language Acquisition. Previous studies have discussed the system itself, its basic concepts and their relationships to such affective variables as anxiety in various L2 learning contexts. The findings of these studies suggest that (1) having a clearer image of one's ideal L2 self might facilitate motivated L2 learning behaviour, (2) affective variables can promote or hinder learners' will to envision their ideal L2 selves, and (3) the system has both theoretical and pedagogical implications for L2 learner autonomy. The present survey study aimed to validate the system among Japanese English as a Foreign Language (EFL) learners in two groups, whose learning contexts made it respectively easier and harder to formulate a clear image of an ideal L2 self. Survey data were analysed using multiple-group structural equation modelling. Results showed that the proposed model fitted both groups, but the relationships among variables in the model were different according to the group. The study also illustrated the dynamic interplay of affective variables (e.g. anxiety, self-efficacy) and the basic tenets of the system thereby providing us with useful insights into L2 learner autonomy.