Player assumes a role of Saya Otonashi — an ordinary schoolgirl, who suffers from amnesia. Upon being attacked by a Chiropteran she learns that she's the only one who can defeat them. She engages in a journey with her family, allies, and her chevalier Haji, to defeat he Chiropterans and recover her identity.

Saya Otonashi, an amnesiac schoolgirl, is attacked by a Chiropteran and learns that she's the only one who can defeat them.