Simon was ignored by the adults of his village and snubbed by the girls, who considered him disgusting. Along with his fear of earthquakes, Simon developed low self-esteem and had many cowardly tendencies. His only friend and role model growing up was Kamina, a brash and eccentric older boy who had an obsession with escaping the underground world for the surface, which he visited as a child with his father. Simon was slowly "recruited" into Team Gurren along with several other boys, and lead by Kamina made several attempts to reach the surface over several years. During one attempt, a sudden earthquake trapped Team Gurren within a chamber and cut off the supply of oxygen. Simon began to panic, but after inspiration from Kamina he managed to dig all of the Team Gurren members out of danger. Yoko would later recall that Kamina himself was terrified during this incident, but he hid his fear from Simon knowing Simon was the only one capable of rescuing his gang.
One day during the digging of a new tunnel, Simon discovers a small drill-shaped object that periodically glows. Later that day, he unearths a large "face" in the ground, which he shows to Yoko and Kamina after Jiiha Village is attacked by a large Gunmen. The face is revealed to be a miniature Gunmen, and the object Simon dug up the key to starting it up. With the aid of this mech, which Kamina names "Lagann", Simon destroys the large Gunmen attacking Jiiha and rises to the surface world.