After meeting with Amber, Hei learns that against common knowledge Contractors can become more humane than was thought to be possible. Realising his own position between the world of contractors and humans, Hei has to make the decisive choice for both. With final farewells to his past comrades inside the Gate, and their support behind his back, Hei's decision brings new future for the world.

An Eurasian girl named Suou watches a meteor shower along with her twin brother Shion and their father, but things go awry when a meteor crashes into their location. Two years later, Shion has turned into a contractor from the incident, confined to a wheelchair due to his renumeration. He is locked away into the family home for safekeeping, while Dr. Pavlichenko spends his time researching into his son's condition and the contractors, forbidding Suou to talk or see her brother. Things go normally in their lives until Suou's best friend Tania becomes a contractor and attacks her boyfriend Nika when he stops her from leaving. Hei aka BK-201 reappears in Russia after a FSB squad tries to capture Shion alive; April also reappears in Russia on a mission to secure Shion.

In Japan, Suo begins honing her combat skills under the watchful eyes of Hei and July. Meanwhile, Kirihara - still puzzled BK-201's disappearance - gets acquainted with the agents of Section 3.

Kiko and Kurasawa help Suo search for her mother. After a mysterious stranger points the young Contractor in the right direction, a long-awaited reunion leads to an unbelievable revelation.