Akiyuki was living a peaceful life along with his friends and family on Sentan Island. This peace was disrupted when sudden war broke out and a strange force took control of his body.

Transformed into Xam'd, Akiyuki confronts the enemy invasion in order to protect his friend Haru. Afterwards he is retrieved by the mysterious Nakiami and taken to the postal airship Zanbani, where she lives.

Nakiami performs a special treatment to contain the power of Xam'd in Akiyuki's right arm. At the same time his family and friends look for his whereabouts.

While becoming accustomed to his new environment, Akiyuki begins the distinctive training in order to control his powers.

Nakiami meets some old acquaintances of hers, and the rest of the crew wonders if she will leave the ship to join them. Meanwhile, a classmate of Haru and Furuichi who lost her entire family surrenders herself to despair.

Akiyuki receives Haru's letters and after learning that she will be waiting for him at Tsumebara Pass, he leaves with Roppa to meet her. However, he encounters more people turning into humanforms along the way.

Akiyuki and Haru meet again in at Tsumebara Pass, but their reunion is cut short by an angry Furuichi who confronts him after discovering that he became a Xam'd.

Raigyo asks for the crew to take a picture together while Haru decides to follow with her military career.

After the incident at the Zanbani, Nakiami decides to return to her homeland and Akiyuki asks to go with her. Meanwhile, Haru pays a visit to Furuichi and finds that he too, became a Xam'd.

Akiyuki loses his sense of self, and with his Xam'd mask permanently affixed, he is captured by a slave trader. Meanwhile, Nakiami continues her journey and meets Yango, a young boy who also became a Xam'd.

Nakiami and Yango continue their journey while the southern army starts to perform experiments on Haru's younger sister, and a mysterious creature persuades a kind old woman to buy Akiyuki from the slave traders.

Nakiami and Yango leave the Tessik village only to see it attacked by a fleet of airships. Akiyuki and Haru meanwhile search for the entrance to the Quickening Chamber