The Third Sister

Thirty years have gone by since Saya went to sleep and Diva was killed. The twins have grown substantially and are fully grown. There is also a surprise awaiting Saya upon her awakening. This surprise came in the form of a second sister. Her name is Eve and she is a bubbly bundle of happiness. Will she pose a threat and how was she found? Where did she come from and why doesn't Saya have any memory of her.