Joey Toy is a youth laboring as a desert mechanic on sand tanks, including the vehicle used by the protagonist and her AI companion. He encounters the protagonist during her desert travels. Joey aspires to emulate his mentor, the experienced mechanic Zankan, whom he calls "Pops." To achieve this goal, he attends technical school while providing mechanical work and maintenance for the protagonist's team.

Joey develops distinct romantic feelings for the protagonist, often displaying jealousy during her interactions with a mysterious male companion. Later, while attempting to invent mechanical improvements for the protagonist's sand tank, he defies the sacred Technos Taboo – a strict prohibition on specific technologies enforced by the ruling class, The Third. This transgression carries severe consequences, resulting in his permanent ban from working as a mechanic, irrevocably ending his professional aspirations.

Joey also exhibits a protective attitude toward Millie, the young daughter of his late mentor Zankan. After Zankan's death, Millie travels with the protagonist's group, and Joey's supportive interactions with her foster a near-sibling bond within the team.