Utsusemimaru (空蝉丸?), nicknamed "Utchy" (ウッチー?), is a Sengoku Period-era Samurai who was trapped in the sentient Raging Knight Dogold armor for 400 years. He assumes the role of Kyoryu Gold (キョウリュウゴールド Kyōryū Gōrudo?) with his partner, the Zyudenryu Pteragordon.
During the Sengoku Period, Utsusemimaru had served under a lord named Moshinosuke Iwaizumi, who had made the future Kyoryuger a samurai despite his background as a commoner and a ronin. When the Deboss Army attacked Japan in an undisclosed time either before or after Utsusemimaru bested Zyudenryu Pteragordon, Torin had asked Moshinosuke Iwaizumi for Utsusemimaru's power to fend off the Deboth Army, which was granted.
During one fateful battle with the Deboth Army, Utsusemimaru saw a Debo Monster with a carp banner kidnap a child on the battlefield, to which Utsusemimaru had foiled. Undoing his transformation, he tried to stir the child, unknowing until the last second of the ingenious trap the Deboth Army had made for him, with the boy actually a Zorima in disguise about to cut him down. However, Moshinosuke Iwaizumi threw himself to take the blow meant for Utsusemimaru, grievously wounding the lord. Slaying the Zorima out of rage, a distraught Utsusemimaru watched on as Moshinosuke Iwaizumi passed away in his arms minutes later after the attack after leaving some final words.
Without their lord, Moshinosuke Iwaizumi's remaining forces were later killed off by the Deboth Army, including Utsusemimaru's human partner Jurota.
With Torin captured and about to be executed by Dogold, a vengeful Utsusemimaru changed into Kyoryu Gold and saved Torin's life. However, Dogold attempts to escape into a dimensional portal and Utsusemimaru gives chase, only to be absorbed by the armor itself.
After the fateful day four centuries ago, Dogold returns, but not as Kyoryu Gold, which causes Torin to question what happened to Utsusemimaru. After a heated battle, Kyoryu Red breaks Dogold's mask, revealing the face of Utsusemimaru.
With the quick thinking of Amy, Torin, and Ramirez, Utsusemimaru was able to escape from Dogold's armor and transforms into Kyoryu Gold, free from his centuries-old spell, and defeats the remaining Knights and the remaining Cabrima, showing the Kyoryugers why he is nicknamed the Thundering Brave (雷鳴の勇者 Raimei no Yūsha?).
After the fight, the other Kyoryugers approach him and cancel their transformation, making Utsusemimaru remember his slain lord Moshinosuke Iwaizumi when he saw Daigo's face. Remembering his last words that his kindness would get him killed, Utsusemimaru had constructed a mask of cold aloofness and brushed off the Kyoryugers.
Utsusemimaru still helped the the team whenever he could, though he retained his coldness. But the continuation of the cold mask eventually made him feel exceptionally guilty, and was soon discovered of this by Amy. After the Horned Brave shared an ice cream cone with him, the samurai confessed his past and why he created a mask of coldness.
Utsusemimaru joined the other five Kyoryugers to get to Deboth but stopped to prevent Raging Knight Dogold and Resentful Knight Endolf from stopping the rest of the team. Utsusemimaru fought the two knights for long time but was caught by Endolf. When he is seemingly about to be killed by Dogold, Endolf was slashed instead. Dogold and Utsusemimaru makes a temporary alliance and when their attacks don't work, Dogold becomes the armor of Utsusemimaru and combines their attacks and defeats Endolf. After the battle with Endolf ends, Dogold challenges Utsusemimaru to a final battle with Dogold being truly destroyed by Utsusemimaru. He then afterwards falls to the ground from being struck by Dogold. He was later revived by his teammates melody.