Yuuji makes the unexpected decision to pursue promotion within the institution he works for. He meets with JB to discuss the documents he submitted for review as a part of the promotion process, documents pertaining to his own past.

Asako Kusakabe rescues a young Yuuji from terrorists on a certain mission. She has evaded death as a soldier time and time again, and on a whim decides to become Yuuji's guardian. Although she partially forces it, and despite her coworker JB's concerns, the awkward female soldier and young man begin to live under the same roof.

After Yumiko gets in touch with the informant "Jimmy," she and the other girls at Mihama Academy learn that the current situation is even worse than they thought. Although they have lost Yuuji and have been driven from the academy, they secure a new base of operations and plan a rescue mission for him.

A formless supporter, "Thanatos," suddenly supports Amane and the others. "Her" objective is also to liberate and rescue Yuuji Kazami. Thanatos and the Mihama girls' interests align and begin preparing to execute their mission. The girls are perplexed by Thanatos's seemingly cryptic instructions that unfold via cell phone, but they bring the girls better results than they ever expected in bringing their goal to fruition.

The international terrorist Heath Oslo uses nuclear weapons as a shield to threaten the nation. The nation plans to make Yuuji a human sacrifice in their dealings with Oslo. There is no other way to save Yuuji from this crisis but to rescue him as he is transferred from Ichigaya to Akasaka.

Tartarus, a gigantic, man-made island, floats on the Pacific Ocean. It is both the adversary of society, and the castle of Heath Oslo, Yuuji Kazami's mortal enemy. Oslo quietly awaits the moment Yuuji Kazami, the final key he needs to fulfill his ambitions, appears before him once more.