Miyu first appears as a classmate of Mai Tokiha. She is the adopted daughter of Father Joseph Greer of the Fuuka Academy Church. She is also the guardian of Alyssa Searrs, a pupil at the Academy's grade school and a talented singer.
Miyu is later revealed to be an android created by Father Greer, who has been working for the Searrs Foundation. It also transpires that she is charged with the welfare of Alyssa, a fake HiME created by the Foundation as part of their goal of controlling the HiME Star.
Miyu causes the first "death" of a Child, defeating Akane Higurashi's Child, Harry (Hari) with an anti-materialisation weapon located in her arm. This causes the disintegration of Akane's lover Kazuya Kurauchi, demonstrating the consequences to the Most Important Person of a HiME if the HiME and her Child are vanquished.