Jacques Yvain founded the manufacturing company Rebuild and created the revolutionary automata, the DZs. His technology ushered in a new era of automation, significantly advancing civilization. He is Derrida Yvain's father, though their relationship is strained due to Derrida's conviction that Jacques values the DZs above family. This conflict intensifies when Jacques accepts a bribe from their superior, Hans Andrei, to reject a critical patch fixing a dangerous flaw in the DZs' programming.

Jacques is assassinated by Andrei's agents immediately after Derrida attempts to deliver the patch. His murder makes him a casualty in Andrei's conspiracy to conceal the DZs' defects and enable their weaponization. Andrei's plot also frames Derrida for the killing.

Jacques's legacy directly fuels the series' central conflict. The unresolved flaw leads to the DZs' militarization and global devastation after Derrida emerges from a decade-long cryogenic stasis. Jacques's choices and their consequences drive Derrida's mission to correct the DZs' programming and fulfill a promise to his colleague, Nathan Bilstein.