Ichirou Sumishiba is a rival to the protagonist Reiji Ozora and initially appears as an antagonist working for the organization known as RI-ON. He is a young man who wears glasses with rectangular frames and has black hair that curls outward, often dressed in a red shirt with a green jacket and light green cargo pants, with a small mole below the corner of his left eye.

Ichirou is defined by the immense pressure he feels to meet his family's high expectations, which drives his primary motivation to defeat the top player, Hikaru Himuro, and claim the title of the number one Dragon Drive player in the world. This ambition leads him to adopt a confident, often arrogant attitude, and he has a notable habit of declaring that he will defeat his opponents within ten minutes.

Despite his initial role as a rival, Ichirou's character evolves beyond simple antagonism. He develops a very close and encouraging relationship with Agent L, a figure within RI-ON who pushes him to be the best. His motivations become more complex when he later joins forces with Reiji, revealing that his previous alliance with another character was a means to rescue Meguru, who is Agent L's younger sister, and bring her back to the real world. He forms a deep friendship with the other main characters and ultimately fights alongside them against the great dragon Shinryu. His character continues to mature, becoming less arrogant and more thoughtful, caring deeply for his friends.

In terms of abilities, Ichirou is a skilled Dragon Drive player who is capable of controlling a series of different dragons. His primary dragon partner is named Hayate Slash. He also commands other dragons, including the dark-elemental Speed Dream Dragon, which possesses unique powers of illusion, hypnosis, and the ability to appear in a person's dream world.