General Gigaro is a member of the Jamahl and a major antagonist in Juukou B-Fighter. He heads the Jamahl's Synthoid-Beast Army, which is comprised of monsters created from Gigaro's blood. He wielded a white bone-like sword and his whale-flatop could open to reveal a gun. He later empowered himself to assume a stronger form called Final Gigaro.
Gigaro was originally a skeletal creature who lived on a desert planet in the Garo dimension. He was frequently hunted by humanoids. Eventually, exhausted and near death, he was found by Emperor Gaohm, who provided him with a new powerful body in exchange for him joining Jamahl.
He accompanied the Jamahl army when they went to invade Earth and was sent by Emperor Gaohm to lead an attack alongside Jera and Schwartz to take over a research building and convert it into the Jamahl's Earth headquarters. Along the way, Gigaro and the Jamahl forces kidnapped numerous humans to use as slaves for the Jamahl. Two of the humans they captured, Daisaku Katagiri and Rei Hayama, resisted after the Jamahl forces attempted to kill a little girl's pet bug, but both were easily put down by Saberizer and tied up to be executed. However, the wise bug sage Guru teamed up with the Earth Academia to combine the power of insects with human technology to create a weapon capable of fending off the attacking Jamahl, the B Commanders. After Takuya used his B-Commander to become Blue Beet, Daisaku and Rei were freed and given B-Commanders to become G-Stag and Reddle. Together, the three formed the B-Fighters and destroyed Saberizer.
After Gaohm became increasingly frustrated with his commanders' continued failures to defeat the B-Fighters, Jera convinced Gigaro and Schwartz to work with her to modify her defeated mercenary Death Mult so he possessed powers from all three armies, resulting in him becoming Phantom Death Mult. After Phantom Death Mult was destroyed by the B-Fighters following a tough battle, Gaohm opted to give his three executives a final chance to prove themselves and sent each of them down to fight one of the B-Fighters. Gigaro faced off against G-Stag in a one-on-one duel and was fought off. He and his fellow commanders later witnessed Gaohm's fight against all three of the B-Fighters and his seeming demise, only for him to return as a massive torso floating in space and recall all three of them to the Jamahl Fortress.
Gigaro later empowered himself with life energy to transform himself into Final Gigaro to fight the B-Fighters. However, he was defeated by Super Blue Beet and killed by Gaohm so the emperor could use Gigaro's life energy to speed up the completion of the Jamahl Hole.
Jagul, later attempted to revive and absorb Gigaro but was foiled by Mai and Kabuto, leaving Jagul with a weak point on her new body.