Masamitsu Seki is one of the officers who befriended the children and assumed one of the empty places in Zearth's group. He joined the military thanks to his fascination with Idol Defense Force Hummingbird.

Spoiler

During Kanji's battle, Seki sacrifices himself in order for Kanji to defeat the enemy robot, creating another empty seat in the group. In the anime, Seki threatened Koemushi with a gun and gets his right arm cut off by him, when he teleported his whole body, except for the hand which was holding the weapon to another place. By the time he signed the contract along Tanaka, it was already replaced with a mechanical prosthetic, which hides some sensors planted by Kanji's mother in order to gain access to information regarding Zearth's technology. In the end, he becomes the only contracted pilot to survive the battles.