Whilst investigating a sudden mass swarming of insects, researcher Takuya Kai of the Earth Academia meets the mystical Insect Elder Guru. He tells him that the insects sense the invasion of the extra-dimensional Jamahl Empire, and are preparing to fight them. With Guru's help, Takuya and his mentor Professor Mukai develop three Power Armor suits infused with the power of beetles. One suit is entrusted to Takuya, the other two to Daisaku Katagiri and Rei Hayama. They become the B-Fighters, who regularly oppose the schemes of Jamahl and its three generals.
- Takuya Kai/Blue Beet: The Leader; an insect researcher from Earth Academia who is the first to learn of Jamahl's evil schemes.
- Daisaku Katagiri/G-Stag: Big Lancer; a tree doctor who claims to hear the voices of trees.
- Rei Hayama/Reddle: Fragilistic Chick; an animal instructor. She left to do animal research in South America and was replaced by Mai Takatori.
- Insect Elder Guru: The Mentor.
- Kabuto: Essentially, the fourth B-Fighter; Guru's Beetle-armored son who left him to pursue a career as a weapons supplier.
- Emperor Gaohm: The Big Bad
- Jera: The Dark Chick
- Schwartz: The robotic Evil Genius
- General Gigaro: The Brute
- Sorceress Jagul: Another Evil Genius; the Sixth Ranger responsible for Shadow's creation. Actually killed off shortly after, but comes back once every other villain is dead.
- Shadow/Black Beet: Takuya's Evil Twin.
Juukou B-Fighter provides examples of the following tropes:
- All Your Powers Combined: Jagul absorbs the powers of various monsters to assume her One-Winged Angel form.
- Back from the Dead: Jagul revives Bill Goldy and Queen as pawns near the finale, then absorbs them into her One-Winged Angel form.
- Bad Boss: Gaohm's methods for completing the Jamahl Hole end up costing Gigaro and Schwartz their lives. He also kills Jera for seeing his true form.
- Berserk Button: Do NOT attempt to cut down a tree when Daisaku is nearby.
- By the Power of Grayskull!:
- "Juukou!" ("Heavy Shell!")
- "Jakou!" ("Evil Shell!") for Black Beet.
- Calling Your Attacks
- Crossover: The final episodes featured Blue SWAT and Janperson aiding our heroes.
- Dragged Off to Hell: Jagul gets this from Bill Goldy in the finale.
- Dragon Their Feet: Jagul comes back in the finale to serve as the Final Boss.
- Drop the Hammer: The motif of episode three's monster.
- Everything's Better with Spinning: The B-Fighters' weapons all spin when activated.
- Grand Finale: With shades of Fully Absorbed Finale, as Janperson and Gun Gibson, plus the Blue SWAT team, all assist the B-Fighters in the final battle.
- Green Aesop: Although it decreases over time, the show often focused on damage being done to the environment, with most of the B-Fighter's weapons and equipment being infused with insect powers.
- Humongous Mecha: The Beet Machines, a trio of beetle-themed vehicles, and Mega Heracles, a gigantic mechanical Hercules beetle.
- Japanese Beetle Brothers: Blue Beet and G-Stag are a Type A.
- The Man Behind the Curtain: The Gaohm we see for most of the series is actually a dummy, with the true Gaohm being an entity contained in a tank full of liquid.
- Mid-Season Upgrade: Blue Beet's Beet Ingram gun, which allows him to transform into Super Blue Beet.
- Mind Screw: The Gaohm Zone. The fight scenes which take place in it range from slightly weird to flat-out insane. Some parts (such as one instance where G-Stag ends up getting randomly slashed with switchblades on a busy street) are outright bizarre.
- Monster of the Week: Some of the most awesome Kaijin in the Metal Heroes franchise appear in this show.
- Mooks: Jahmal's Jamars.
- Noble Demon: Black Beet
- One-Winged Angel: Jagul turns into her "Destruction-God" form, fusing herself with various destroyed monsters, as well as a few villains from Janperson and Blue SWAT; it takes Super Blue Beet, Hyper Shou's DrumGunner, and Janperson's Flash Cannon, and being Dragged Off to Hell by Bill Goldy to defeat her.
- Omnicidal Maniac: Gaohm plans to use the Jamahl Hole to destroy the Earth in order to summon Saint Papilia so he can capture her to gain immortality.
- Out of the Inferno: Pulled by the B-Fighters in episode three, when walking out of a destroyed building.
- Powered Armor: The B-Fighters' Insect Armor.
- Power Trio
- Super Soldier: The Toku version since Metalder.
- Super Strength: One of the powers given to the B-Fighters by their armor
- Synchronization: Whenever Shadow hurts Takuya, or vice-versa, they each feel the pain.
- Transformation Trinket: Handheld devices called the B-Commanders.
- You Have Outlived Your Usefulness: Jagul pulls this on Goldy and Queen in the finale.