Masamitsu Seki is one of the officers who befriended the children and filled one of the vacant spots in Zearth's group. His interest in the Idol Defense Force Hummingbird led him to join the military.
During Kanji's battle, Seki sacrifices himself so that Kanji can defeat the enemy robot, leaving another vacancy in the group. In the anime, Seki threatened Koemushi with a gun but had his right arm severed by him when he teleported his entire body except for the hand holding the weapon to another location. By the time he signed the contract alongside Tanaka, his arm had already been replaced with a mechanical prosthetic. This prosthetic conceals sensors planted by Kanji's mother, allowing access to information about Zearth's technology.
In the end, he becomes the sole contracted pilot to survive the battles.










