Diva  

, ディーヴァ

Diva is Saya's twin sister who serves as the main antagonist in the story. She was born in 1833 and was kept isolated during an experiment that resulted in her being able to produce Delta67, a substance used to transform people into Chiropterans. Despite her traumatic upbringing, Diva harbors a deep-seated hatred for Joel, which led her to brutally murder him and his friends at his birthday party when Saya freed her from captivity. As a result of her isolation, she is socially inept and lacks an understanding of the moral implications of her actions.