Bust Through the Heavens with Your Drill!!

S1, E1: Simon, a boy who had been digging new tunnels to expand his village, comes across a small drill that glows mysteriously. Kamina, Simon’s surrogate older brother, believes in the existence of a “surface” world above and has been scheming to escape there. One day, an earthquake causes the ceiling to collapse and a gigantic mecha falls into the village. Kamina recklessly tries to oppose the rampaging mecha. As he does, Yoko, a girl with a rifle, appears in pursuit of the mecha called a “Gunmen.”