April. A second year high school student, Arato had a normal life he spent with his friends Ryo and Kengo. Until that night. On his way home from shopping, Arato is attacked by a corrupted hIE, but a beautiful hIE named Lacia comes to his rescue.

Arato manages to rescue Kengo from the calamity at the industrial promotion center. However, even after returning to normal life, he finds himself consumed by the ever deepening mysteries. Meanwhile at the Memeframe Corporation, a factional dispute becomes escalated. Within the upheaval, the Lacia-class hIE Methode is about to make her move.

After being summoned by Erika to the Burrows estate, the Lacia-class hIE's fight entered the next phase. As each of them contemplated their next move, Kouka felt her possibility for a future quickly closing as she was being pursued as a suspect in the Chubu Airport bombing by the security police.

It has been two months since the tragic events in Mitaka. The world returned to some semblance of normalcy, and Arato and Lacia lay low as they prepare for whatever may come next. However, their brief period of happiness is disturbed after they are contacted by the super intelligent AI Astraia.

Arato and Lacia walk towards the heart of the Higgins storage facility in order to choose a future. The two act like one as they help and support each other. However, damaged from the intense battle, Lacia does not have much time left...