Professor Kenzou Mukai An old man dedicated to the pursuit of justice. He worked as a mentor for the B-Fighters, usually working at Earth Academia to assist the team by leading research on Jamahl's warriors and developing new weaponry and vehicles for the B-Fighters. He fell in love with Sayuri, a plant researcher, many years ago, but left her. When they met once again during Rasbelga's attack, Mukai donned a special armor and donned the title of "Mukaider K-3" to save her.

Insect Elder Guru The elder of the insect tribe, and looks like a giant yellow rhinobeetle. He carries a staff with a curled top. Guru possesses great the mystical power of his own. Takuya bumped into him inside of a cave, when he appeared to him. He gave the B-Fighters their powers.

Muscle Muscle was a mysterious armored amphibious alien who arrives on Earth with a shining feather that belongs to Saint Papilia. He was once healed by her power, and had followed clues about her to Earth. Muscle was defeated and Black Beet gained possession of Papilia's feather. He appeared in Episode 40.

Saint Papilia A legendary 'butterfly of life' who can grant immortality. She appears when the life on a world has been diminished. She then revives the world by giving it new life. Saint Papilia already appeared once on Earth, after the Ice Age, and revived the Earth so the life of today could be born and grow. Saint Papilia has also revived Muscle during the course of her existence. Both Gaohm and Black Beet sought Saint Papilia in the hopes of obtaining her gift of eternal life. After Takuya defeated Shadow, he was severely wounded and died. Saint Papilia appeared above him and resurrected him, saying that Earth still needed him.

Tokusou Robo Janperson and Gun Gibson The robotic detective heroes from their respective Metal Heroes series Tokusou Robo Janperson, they appeared and assisted the B-Fighters in their battle against Jagul at the end of the series.

Shou, Sig and Sarah (Blue SWAT, Grey SWAT, Purple SWAT) Trio of special, heavily armed alien-destroying heroes from the Metal Heroes series Blue SWAT. Sarah and Mai were captured by Jagul, and Shou and Sig, along with Janperson and Gun Gibson, aided the B-Fighters to rescue them.

B-Fighter Kabuto The next generation of B-Fighters 10 years later. The original B-Fighter go to assist them in the search for eight powerful medals but are infected by a virus that makes them fight each other. When the virus is frozen, they able to overcome it.