Daichi is a 17-year-old high school student who lost his father years prior in a space travel accident and left his family's home on Tanegashima afterwards. When he sees a ringed rainbow formation on a television broadcast from the Tanegashima Space Center, he returns. Because of his skill at a particular arcade game, it makes him the perfect pilot for the Earth Engine Impacter and the smaller Earth Engine Ordinary component robot. Daichi is able to summon a mysterious laser handgun known as the Livlaster Tanegashima, a powerful weapon that utilizes pure Orgone energy, which is essential for piloting the Earth Engine. Later he is assigned the title of "Captain Earth", the leader of the Midsummer's Knights.
Daichi is uncomfortable with his new title and the responsibilities that come from being a "Captain" like his father. The Planetary Gears refer to Daichi as a "Neoteny."
Daichi wears a white and red flight suit on missions, matching the Earth Engine's paint job.