1 (クォンタムデビルサーガ　アバタールチューナー I, Kuontamu Debiru Sāga Abatāru Chūnā I, Quantum Devil Saga, Avatar Tuner I) is a 2011 science fiction novel by Japanese author Yu Godai, the first in a series of five installments.

[2] In the post-apocalyptic Junkyard, warring tribes vie to unify the six territories and thus gain entrance to Nirvana, the promised land.

When a mysterious object appears in the Junkyard, it incites a battle between the Embryon tribe and the rival Vanguards.

In the aftermath of this firefight, Serph discovers a mysterious girl named Sera, and finds that he and his closest warriors have gained the ability to transform into powerful demons.

The Embryon must adapt to these developments and try to understand their meaning as the balance of power begins to shift in the Junkyard.