In a world where unseen beings known as Jiex (Has Physical Form) secretly coexist with humanity, a hidden war rages beneath the surface. These entities form contracts with humans through emotional resonance, allowing them to survive undetected while influencing the human world from within.

Kuroihana Shinchiro, a former delinquent burdened by a life of constant misfortune and violence, seeks nothing more than peace. But after reaching his breaking point, a near-fatal incident triggers an abnormal contract with a high-ranking Jiex known as a Daijiex—Kyoha.

Unlike ordinary contracts, their bond defies the natural order. They exist as equals, sharing power while maintaining separate bodies, bound by a connection neither fully understands. As Shinchiro begins to awaken to his own transformation into a Daijiex, he becomes a target of both humanity’s Jiex Elimination Force and the Jiex themselves.

Branded as “Akuma” (Taken from The name of his Daijiex Full Transformation armour)— a devil feared by society — Shinchiro walks a path between two worlds, while Kyoha, experiencing human life for the first time, begins to discover emotions she was never meant to have.

As their journey unfolds, they encounter others bound by similar contracts, including Tashigi, a man driven by revenge and loss. Allies and enemies blur, and the line between human and Jiex begins to fade.

In a story that blends action, mystery, and quiet moments of humanity, Jiex: Existential Number 002 explores the meaning of existence, the weight of identity, and the unexpected possibility that even beings born as enemies may learn to understand—and even love—one another.