One day, Saku was the target of a terrorist attack. She was saved by Shinri, a fellow student. He vowed to do things under his accord and bring change to the school. Saku decided that she must keep an eye on him.

A virtual world. Gunshots and bombs. A ruined city. Yet the only thing Kou remembers is the name of a case: "Gray Christmas". As the whole history about it comes back to him, his peaceful days come to an end.

Hayato has a special magic ability, but since it can only be used within 10 seconds, it's not really useful to him. Freed from a rough upbringing in an orphanage, he was glad to finally start a new life. However, these halcyon days would soon be shattered when the orphanage director came to take his daughter away.

Kamishiro Nao, a dropout of his high school's athletics club, confesses his love to his senior and club manager Koga Sachi but is rejected. In despair, he wishes for the world to end, and shortly afterwards the Koushin singularity disaster strikes and annihilates the small town Nao and Sachi reside in.