A VOW THAT CANNOT BE BROKEN!Itu2019s been years since the kihei appeared without warning and overran the earth. To combat this threat, humanity established the Twilight Academy to train students as soldiers, though most die before graduation. During a mission, Kou Kagurou2019s squad is attacked, and he must face his fate as yet another student casualty…or so he thought. A girl in white appears during his final moments and swears to protect him, filling a hole in his heart and setting them both on a path of love and despair.

After taking a kihei as his Bride and overcoming the massive invasion known as the Gloaming, Kou Kaguro has finally earned some peace for himself and his friends. But as they take in the festival commemorating this hard-won victory, the unthinkable happensu2014Kou is murdered. It happens over and over, no matter how many times he turns back the clock. As if that werenu2019t enough, Pandemonium faces a whole new threat in the form of the strongest class in Combat, the Puppets. Who really wants Kou dead, and why…?

After narrowly avoiding a terrible fate at the school festival, Kou renews his friendship with his old classmates from Research, Asagiri and Isumi. As they pass the time in peace, Asagiri decides to confess her love for Kou. However, the very next day, Isumi informs Kou that Asagiri has disappeared in the kihei-infested ruins! As he searches for her, a new threat arises, which may shed light on the true nature of the kihei. For the sake of his beloved Brides, Kou must make a choice.