Sadamitsu the Destroyer

Sadamitsu the Destroyer (破壊魔定光) is a manga series by Masahiko Nakahira. It was adapted into a 10 episode animated series.

The story stars Tsubaki Sadamitsu, a young delinquent and leader of the Corpse Gang, who after a chance encounter with an alien robot is forced to take up the task of capturing Rukeitai (intergalactic criminals). His job is made harder with the appearance of the Vulture, a last ditch effort to keep the Rukeitai under control.

An English adaptation of the anime was released in North America by Media Blasters in 2003.

Characters
The hot-headed, fight-enjoying main character. While he loves a good fight, he detests pointless cruelty and never kills. His preferred weapon is a bokken (wooden sword). In combat, he wears the sentient helmet nicknamed 'Junk' and wields an energy weapon that seals the Rukeitai away.
 * Sadamitsu Tsubaki (椿 定光):

Originally a robotic 'space cop', 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. While severely damaged towards the end of the anime, upon his revival he increases Sadamitsu's strength even further, adding new weapons to his arsenal. While his name is unknown, Sadamitsu refers to him as 'Junk' while other characters refer to him as 'Helmet', 'Helmet-san' (Mr. Helmet) and the like.
 * Junk (ポンコツ):

A strange girl in Sadamitsu's class, Yayoi has many secrets about her. She also knows something about Sadamitsu's past and appears to be attracted to him, though she weirds him out. She is also a controller of Vulture. It is later revealed that she and Sadamitsu were childhood friends until the Vulture accidentally killed her upon arrival on Earth. Because the Vulture also lost its host body, it revived and possessed Yayoi, erasing Sadamitsu's memories about her. Meanwhile, it kept Yayoi's memories, ultimately resulting in the Vulture proceeding to hunt down the Rukeitai rather than simply destroying the entire planet, due to its new host's affection towards Sadamitsu.
 * Yayoi Kamishiro (神代やよい):

Falsely banished as a criminal, Kulon landed on Earth among the other Rukeitai. Being a speedster, stated to being the fastest in the universe, he caused some ruckus while being chased by the police. He was arrested in the first place because he enjoyed giving other beings the same feeling he had with his speed, but unknowingly gave a ride to criminals. Ultimately, he was taken in by Sadamitsu, where he served a role similar to that of a sidekick's, usually being used as a motorcycle. He proves to be very loyal, as he obeys Sadamitsu's requests even when he is obviously frightened.
 * Kulon (クロン):