Siren (2015)

Original title: サイレーン

Satomi Shinobu works in the Mobile Investigation Unit of The Tokyo Metropolitan Police Department. The Mobile Investigation Unit conducts the initial investigation at all crime scenes. He works with Inokuma Yuki. They are a couple, but they keep their relationship a secret at work. They both hope to work at the #1 Investigation Station. One day, they meet beautiful Tachibana Kara at the site where a dead body was found. Kara appears at the other crime scenes involving grotesque murders. She shows an interest in Yuki. Satomi Shinobu thinks it's a bad sign for Yuki. To protect his girlfriend from danger, he struggles to find uncover the truth behind the serial murder cases and Kara’s identity.