While possessed by Dragold, Rudy was considered the main antagonist of the first season.
Rudy is a short preteen boy often seen with a kind expression on his face. He has short light brown hair and green eyes. He wears a white jacket with red sleeves and black collar. Underneath, he wears a light blue shirt. He also wears dark blue pants that reach up to his ankles and that which has a yellow handkerchief in its pocket. Lastly, he wears a pair of predominantly yellow sneakers.
While controlled by Smash Dragold, Rudy's light brown hair blazed into spiky blonde and his face is now noticeably overconfident.
In his debut all up to the events leading up to that incident in the North Sumadora Ruins; Rudy is an optimistic and enthusiastic boy with great admiration for Riki. Rudy would even go as far as to dare the blizzards of the Northern City just so that he can follow up to Riki. Despite that, Rudy is not a regular fanboy, because he is a highly skilled and impressive player, as he had exhibited during the West City Grand Prix and in the Park Exhibition Match against Riki and Simon.
However, deep within Rudy's idolatry for Riki lies intense jealousy over the fact that Riki has a cooler B-Daman, and that Rudy himself had already desired having his own Dragon-Type B-Daman. When Rudy lost his WBMA Proto 01 inside the ruins, he was totally consumed with the feeling of despair. This is when the spirit of Smash Dragold took advantage of him.
Under the influence of the Legendary Golden Dragon; Rudy is easily said, a power-tripper. He had discarded his bonds with Riki and the others while accepting Novu as his henchman. Eventually, Rudy also discards Novu so that the former can take over the WBMA and the world himself. Rudy's power-tripping is partly because of Dragold's influence and his own jealousy towards Riki. When he was freed from Dragold's mind control, he became extremely remorseful about his transgressions, as evidenced when he started crying.
- His family name "Sumeragi" is Japanese for Emperor while his given name "Ryuji" means Dragon. Altogether, Ryuji Sumeragi means Dragon Emperor. This is fitting for his Dragold-possessed persona.
- He is the only dragon-type user who does not use any Metal/Heavy Cores unlike the other four dragon-type users (Riki, Samuru, Novu, and Basara).
- Defeated by the 4 legendary dragon types (Dracyan,Dravise,Dragren,Drazeros) since the final GP Break Bomber
- Insulted by Alba Cocodoro that Rudy is a faliure to a B-shot