Hideo Torai, a former firefighter, joined the defense organization Grand Paladin after leaving that career. The loss of his mother in a fire during middle school significantly influenced his decision to become a firefighter after high school before transitioning to Grand Paladin. He is an idealistic and good-natured individual who consistently strives to help others, reflecting a well-rounded personality. Physically, he has brown hair and eyes, with three distinctive spots under one eye. His Grand Paladin mecha form is modeled after a tiger, aligning with the group's animal motifs.

During an initial confrontation with Sōya Kuroi, Hideo is defeated and loses his power—a small jar of stardust taken by Sōya. This encounter is part of Sōya's mission against Grand Paladin due to their perceived connection to his home planet's destruction. Following the death of Grand Paladin's original leader, Takashi Ryūzōji, Hideo assumes leadership of the remaining Paladins, tasked with defending Earth from ongoing threats.

Hideo interacts with other Grand Paladin members like Benika Takatori and Yōsuke Hitsujitani. His development involves transitioning from a frontline fighter to a leadership role, emphasizing his commitment to protecting humanity amid interstellar conflict.