Riku Munakata, second daughter of Uchuu Munakata and Sora Munakata, belongs to the powerful Munakata family, renowned for its immense wealth and control over Japan. She has a sister, Umi Munakata. Riku possesses exceptional talent in finance and mathematics, consistently expressing herself in a distinctly intellectual manner. This expertise places her as co-pilot of Arma Zenon, one of the three Zenon Guardians deployed to protect Earth from the invading forces of the Zeno Palace Empire.