Peebo is an android guardian from the Bio Star who arrived on Earth 500 years ago, bringing the Bio Dragon, Bio Robo, and the power of the Bio Particles. During that ancient visit, he showered five courageous humans with Bio Particles, setting the foundation for their descendants to one day become Bioman.

In the present day, Peebo operates the Bio Base and gathers the descendants of the original Bio Particle recipients to fight the Neo Empire Gear. Though gentle and supportive, he carries deep fear of Bio Hunter Silva and the destruction tied to the Bio Star's past.

Peebo ultimately proves his courage by risking his own life to energize Bio Robo during the final battle, ensuring the team can continue fighting when it matters most.

Raised in an orphanage under the name Koichi Nakamura, Shuichi eventually discovers that he is the biological son of Doctor Man and the physical basis for the android commander Prince.

Doctor Man attempts to recruit him into Gear, but Shuichi rejects his father's mechanical empire. He later allies with Professor Shibata and helps the Bioman team fight Gear, ultimately reaching the remaining traces of Doctor Man's humanity during the final crisis.

Setsuko Kageyama is the former wife of Dr. Hideo Kageyama and the mother of Shuichi. When her husband descended into madness and transformed himself into the cyborg Doctor Man, she fled to protect their son.

Seventeen years later, the Bioman team and Shuichi discover a letter and video recording she left behind, revealing the truth of Doctor Man's origins and the tragedy of the Kageyama family.

Shinichiro Gou is the estranged father of Shiro Gou, Red One, and the former research partner of Dr. Kageyama. After Kageyama became Doctor Man, Shinichiro faked his own death and left his family behind so he could dedicate himself to stopping his former friend.

Operating under the alias Professor Shibata, he hides his identity behind rose-colored glasses and a false beard. Cybernetically enhanced and burdened by his past, he plays a key role in developing a conscience circuit capable of giving Mecha Clones independent will.

Joy was a young friend of Peebo from the Bio Star who sent a video message to Earth before the planet's destruction. Doctor Man intercepts the disc and creates a Mecha Clone of Joy to deceive Peebo and locate the Bio Base.

The deception fails when Peebo views the true message and realizes that the real Joy died with the Bio Star. The recording becomes a final farewell from Peebo's lost homeworld.

Ken Hayase is the captain of the Japanese Olympic Archery Team and the former coach of Jun Yabuki. After Jun suddenly leaves her Olympic training, he investigates her disappearance and tries to convince her to return.

When he discovers that Jun has become Yellow Four, he understands the importance of her mission and gives her his blessing to remain with the Bioman team.

Shota Yamamori is a fiercely dedicated protector of nature living in Mount Nekura. After falling in love with Jun, he desperately attempts to join the Bioman team, but Bio Robo detects no Bio Particles within him.

Gear exploits his disappointment, and Farrah tricks him into undergoing a procedure that transforms him into the brainwashed Magne Warrior. Shota eventually breaks free of Gear's control and assists the team. He is notable as an early prototype for the later Sixth Ranger concept in Super Sentai.

Miki is a special Mecha Clone created by Doctor Man in the form of a young schoolgirl. She is directly linked to the Mechagigan Satan Megas, allowing the monster to endlessly reassemble itself as long as she exists.

After Professor Shibata implants her with a conscience circuit, Miki develops human empathy and feels guilt over Gear's destruction. She tragically self-destructs so Bio Robo can finally defeat Satan Megas.