Originally a robotic space cop known to the rukeitai as a "pursuer", Junk's body was destroyed during an encounter with a Rukeitai. His severed head called out to Sadamitsu and, once worn as a helmet, empowered the youth enough to stand up to the superhuman strength of the Rukeitai. Junk gives Sadamitsu the ability to fly and covers his body with a "material guard", which greatly dampens enemy attacks. Also, to take advantage of Sadamitsu's proficiency with a wooden sword or "boktou", Junk has Sadamitsu fire his activator at a lightning rod, which turns it into a sword shaped activator.

Junk has a hard time adjusting to Earth's, or rather Japan's culture and language, especially where Sadamitsu is concerned. His long-winded and technical explanations usually confuse or exasperate Sadamitsu, and so Junk often has to dumb-down his explanations for him to understand.

While his name is unknown, Sadamitsu refers to him as 'Junk', due to his body being mostly destroyed, while other characters simply refer to him as 'Helmet', 'Helmet-san' (Mr. Helmet) and the like. Voiced by: Kazuhiro Yamaji (Japanese), Sean Schemmel (English)