The transfer of human consciousness into a robotic "I-Machine" is now a reality owing to the discovery of a lucrative ore known as "orichalt," but there is a risk that the awareness may not return to the host's body, leaving them trapped inside their new metallic frame for good. This is the condition of members of the Excavate Company, a reckless band of I-Machine miners commanded by the infamous Grayman who seeks to profit from orichalt mining. During a mining raid, the party saves Maya Mikuri, a student who has been abandoned by her team. Her old colleagues accuse her of stealing confidential knowledge about orichalt, so she joins the Excavate Company in the hopes of clearing her record. They then go on an expedition that will transform their life, including that of their children.