BullBlack (ブルブラック BuruBurakku?) is Black Knight I (初代黒騎士 Shodai Kuro Kishi?, 18-25) who seeks revenge on Captain Zahab for the destruction of his homeworld and the death of his younger brother. Although he fights against the Space Pirates Balban, he is not an ally to the Gingamen and the two frequently clash due to BullBlack's willingness to sacrifice innocent people .
During the Balban's initial rampage across space, one of the planets they attacked was BullBlack's homeworld of Taurus. BullBlack attempted to stop them, but was forced to stand down when the Balban took his younger brother Krantz hostage. As the Majjin assaulted him, Zahab decided to show just how weak BullBlack's sentimentality made him and forced him to watch as he personally cut down Krantz in front of him. Consumed by his hatred, Bullblack obtained the Lights of Ginga and followed the Balban to Earth but was forced to release them when he was confronted by Sambash who he tricked into thinking the Lights were hidden in a cave before being dropped into a deep fissure into the Earth. Three thousand years later, as the Balban were released from the seal the original Gingamen had placed them under, Ryouma's brother Hyuuga (who was originally intended to be the new GingaRed) fell into the same fissure as BullBlack. BullBlack rescued Hyuuga and then merged with him in order to use Hyuuga's strength to escape the abyss.
First appearing to rescue Ryouma from Kugutsudayuu's exploding dolls, BullBlack then attempted to steal an artifact called the Oni Stone, believing it to contain the Lights of Ginga. Sensing his brother's presence within BullBlack, Ryouma as well as Saya initially believed that BullBlack was Hyuuga but dismissed it after seeing that BullBlack's fighting style was unlike that of Hyuuga. After the Oni Stone was revealed to be another false lead, BullBlack revealed to the Gingamen his connection to the Lights and announced that he would be the one to claim them.
As Budoh began sending his Four Shoguns after the final four hiding places, Bullblack showed just how far he was willing to go when he opened fire on the Majin Sunabakutou while innocent people were still in the crossfire. Later, as he and the Gingaman engaged Sunabakutou a second time, the Majin took an innocent child hostage and demanded that they drop their swords. Despite the pleading of the Gingamen, BullBlack not only refused to discard his weapon, but advanced forward, saying that the child's death wouldn't matter so long as he still killed Sunabakutou. In an attempt to stop him, Ryouma lept forward and tried to hold BullBlack back, arguing that fighting this way made him no different than the Baluban, granting Sunabakutou the chance to blast them both with his explosive sand attack. While the other Gingaman took advantage of the situation to rescue the child, the sun sculpture Sunabakutou was after revealed itself to be another false lead, causing him to drink his Baluba-X and grow giant. As the first Budoh Shogun proved to be more than the Gingamen and the Seijuu could handle on their own, BullBlack summoned GoTaurus, transforming into HeavyKnight and then combining with GoTaurus to form Combined Beast-Warrior BullTaurus to defeat him. Afterward, the Gingamen tried once again to convice BullBlack to ally with them, but BullBlack said that vengeance was his only goal and called the Gingamen naive for thinking they could defeat the Baluban so long as they valued the lives of others over their own objectives. Meanwhile, Hyuuga's spirit eventually began to rebel against BullBlack from within, subjecting Bullblack to intense pain whenever his personal vendetta put the lives of others in danger.
After losing the Lights of Ginga to the Gingamen, Bullblack enacted a plan to kill the Balban once and for all by blowing up the entire Earth by directly transmitting his energy as BullTaurus into the earth's core. However, GoTaurus had had enough of his master's selfishness and abandoned him, leaving BullBlack defenseless when the Iliess Majin Wangawanga attempted to harvest BullBlack's hatred. Rescued by GingaRed, BullBlack finally revealed to Ryouma how he was using Hyuuga's body and strength to seek his revenge and drew his sword in anticipation of Ryouma's retribution. But despite his goading, Ryouma said that fighting for revenge or sacrificing the life of someone else wasn't the way Hyuuga had taught him to fight and that doing so would only cause his brother sadness. Ryouma then left to aid the others while BullBlack pondered the similarities between himself and Ryouma and how far he had fallen from the noble warrior his young brother idolized. Later, as BullBlack watched the Gingamen attempt to seal the crater he had created, Krantz's spirit appeared before him and helped him realize that even if BullBlack hadn't a planet or people of his own to defend anymore, there were other planets and people that he could defend. With his rage no longer controlling him, BullBlack released Hyuuga and then locked the Gingamen in a protective forcefield before falling into the crater and triggering it to collapse into itself, sacrificing his life in the process. Reunited with Krantz, Bullblack finally found peace although a portion of his spirit remained with the Bull Riot and throught it passed his powers and title along to Hyuuga. BullBlack's spirit would also occasionally speak through the Bull Riot to offer counsel and advice, such as when he told the Gingamen how to transform the Lights of Ginga into the Galeo Pulsar.