Simon's name comes from the Japanese word for "below"



As a boy, Simon is physically underdeveloped for his age (early teens), standing at little more than 5-feet tall. He wears a long sleeved blue and red jacket and brown shorts, topped with a pair of yellow and red goggles and brown work shoes. He has indigo hair and wide eyes with small pupils, and his iris color was eventually revealed to be an almost the same color as his hair. Simon also ties on shin guards and sports a cloth waistband, and the Core Drill hangs from a fastened leather string around his neck. Originally, Simon wore a dusty brown cloak, which eased his passage through the narrow tunnels of the underground, but this cloak was blown off by the wind during the initial escape from Giha Village.
Though valued as one of the most skilled diggers in Giha Village, Simon is ignored by the adults and snubbed by the girls, who consider him disgusting because of his peculiar habits and odd smell. Lacking parental figures to help him mature, along with his fear of earthquakes, Simon is plagued by low self-esteem and has many cowardly tendencies. Even after his friendship with Kamina, he continues to act cowardly and doubts his own abilities. However, Kamina's inspirational speeches gives Simon just enough confidence to endure his fears and to accomplish something. Young Simon is also susceptible to bouts of intense determination, such as when he charged at the Gunzar (later, the Gurren) and the Enki





Simon was born in Giha Village, one of many subterranean civilizations on Planet Earth in the far future. Unlike other villages, Giha Village had supplies of fresh water, animals (Molepigs) for food and electric generators for light. In spite of this, there was an ever-present threat of cave-ins from earthquakes, so the village chief employs diggers from the energetic and maneuverable youth to create new routes for the city to expand. Simon became one of them, and quickly distinguishes himself as one of the best diggers.
At age seven, Simon's parents were killed before his eyes in a cave-in during an earthquake. The incident traumatized him and gave him a phobia for earthquakes. Simon then devoted his entire existence to his job, earning him the scorn from his peers. Only Kamina, the local gang leader and juvenile delinquent, reached out to Simon. Kamina "recruited" Simon into "Team Gurren" by dragging him along on outrageous schemes to escape Giha Village to the surface, which Kamina claims he had visited as a young boy. Though Simon was an outcast, he would always feel more comfortable around Kamina. In one instance, Kamina and the other members were trapped in a small hole caused by an earthquake; everyone was scared, but Kamina's pep talks to Simon motivates the digger to drill a tunnel out of the barricade. After this incident, Kamina and Simon grew so close that they could have been called brothers.
One day, during the digging of a new tunnel, Simon discovers a small drill-shaped object that periodically glows, an item known as the Core Drill. On the same day, he unearths a large "face" in the ground, and shows it to Yoko and Kamina after Giha Village is attacked by a large Gunmen. The face is revealed to be a miniature Gunmen, and the Core Drill Simon dug up is the key to starting it. With the aid of this mech, which Kamina names the "Lagann", Simon destroys the large Gunmen attacking Giha and rises to the surface world.