An assault on a peaceful city of technology by the evil Doctor Man and the Neo Empire Gear awakens an ancient robot, who chooses five humans to awaken into becoming Bioman to face the mechanical invaders.

Doctor Man sends Fara and Psygorn to pursue Mika Koizumi about Bioman, even though she had quit the team while the other members try to win her back onto their side.

When Bio Robo becomes unexpectedly damaged during a battle with a Mecha-Gigan, Shirou tries to get a part needed for repair only to have the powerful Monster standing in his way.

Using Shirou's animal informants, Bioman discovers a Gear plot to replace humans with exploding Mecha Humans to sabotage a super-energy plant.

In order to discourage people from indulging in a rain of coins created by an invisible Mecha Gigan controlled by Monster, Shingo decides to become a bad criminal to get the means to stop it.

Mika's pursuit of a lead when a Mecha Gigant crash lands near a mountain leads her into a confrontation with Fara over a plot connected with a trap by Gear to stop Bio Robo.

When Peebo discovers a letter from a friend from Bio, it inspires Doctor Man to start a plot involving making the robot believe that his friend has returned after 500 years.

As Peebo is forced to give up Bioman's secrets to Gear, the team rescues him as they decide to discover the harsh truth about Joy's ultimate fate.

Ryuuta becomes trapped within the dimension of a supercomputer by twin girl Mecha Humans being used to capture children for Gear.

Doctor Man develops a gun devised of Anti-Bio Particles to destroy the Bio Particles within the Bioman, forcing Mika to make a move that may ultimately prove to be fatal!

After the passing of their teammate, Bioman search for a new Yellow4, all while they're pursued by a mischievous archer who doesn't realize what she's getting into.

Shingo begins to doubt himself when he believes that a Mecha-Human was actually the father of a boy he was trying to save.

Jun tries to figure a way to defeat Gear's newest upgrade on her own while the captain of the Olympic archery tracks her down to find out what happened to her.

When Doctor Man abandons a new Mecha Gigan-controlling super-computer that develops emotions, Hikaru tries to win it over with the concepts of love and empathy.

After being accused by Jun of not doing enough to stop a fungus being distributed by Gear, Hikaru puts it upon herself to find the means to stop their infection plans.

Jun must reach a device that will cause a massive volcanic explosion in 6 hours time, but is distracted by Fara in preventing her from reaching that goal quickly.

Doctor Man orders the abduction of a boy related to Urashima Taro, in hopes of using his ancestor's memory to find the treasures of the undersea utopia.

Shingo encounters a girl who has strange visions of a Mecha Gigan attacking her town associated with a stone that gives her amazing gifts.

Doctor Man adds his 17-year old son to Gear as its new commander, with a cruelty that Ryuuta believes can be stopped.

As the Bioman try to figure out how to deal with Prince and his Grotes Canth, Ryuuta tries to discover how to relate his own experiences in hopes of dealing with Doctor Man's son.

A Mecha-Human photographer set up by Monster takes control of an investigating Hikaru, forcing Jun to pick up where she left off in order to save her and discover the plan.

When Ryuuta gets involved in returning a gold statue to its original owner, it becomes complicated when Fara sends out a Ryuuta Mecha-human to steal gold for Gear.

Bioman must protect a runaway girl who ends up with a gemstone required by Gear to perfect their new super-weapon for causing global chaos.

Shingo tries to protect the flowers of two children after Fara and a Mecha Gigan transform a field they cultivated for sale into bombs set to explode.

Shuichi Kageyama, a boy looking for his family, is attacked by Gear's forces as Doctor Man tries to confirm that he is actually his true long-lost son!

As Doctor Man continues to pursue his son to join him, Shuichi receives a mysterious contact from his mother that leads to the revelation to him and Bioman of the truth regarding Gear's leader.

Hikaru and Jun become trapped in a seaside town conquered by an army of mechanical spiders that control the populace.

Realizing the trouble of Gear being ruled by a human, the Big Three decide to assassinate Doctor Man, leading to a loyal Mechaclone to try and reach a weapon in hopes of dealing with them.

Trying to find a boy's lost brother, Ryuta discovers a Gear plot to suck Tokyo into multiple simultaneous black-hole bombs!

Shirou becomes the fake fiancée of a swordmaker's daughter in order to prevent Monster from obtaining a sword for Doctor Man's final Mecha Gigan.