This research examines some modes of Japanization through education in Okinawa where Japanese influences on education have permeated after Japan's annexation. I investigate how a book excerpt entitled "Mizu no Tozai," included in high school textbooks in Okinawa, constructs Japanese identity. "Mizu no Tozai" functions as nihonjinron discourse, which is characterized by 'Japanese culture,' 'Japanese uniqueness,' and 'Japaneseness.' The 'East-West' dichotomy, depicted in this "nihonjinron" discourse, induces students to choose 'Japan'/'Japanese culture' and become 'Japanese.' Practice sections of "Mizu no Tozai" in textbooks as well as a textbook guide operate to be complicit in this Japanese identity construction. Through a critical analysis of discourse, I reveal that the "nihonjinron" discourse operating as official knowledge, in collusion with the other discursive texts, produces a position subjected to the discourse of Japanization within which Okinawans become 'Japanese.' I problematize these discursive texts as a systematic form of Japanizing Okinawans' minds through education.