 One day, Simon unearths a drill-shaped key called a Core Drill, followed by a small mecha resembling a face called a Gunmen.Shortly thereafter, a huge Gunmen crashes through the ceiling and begins attacking the village, followed by a girl named Yoko, who attempts to repel the Gunmen.Simon uses his Core Drill to activate the smaller Gunmen (which Kamina names Lagann) and its drilling-based abilities.