Ryoma is the eldest son of Sumeragi and Ikona and the eldest child of four in the Hoshidan royal family. When Sumeragi married his second wife Mikoto, Ryoma helped the nation warm up to the new queen by establishing a strong relationship with his step-mother. Ryoma also recognized Mikoto's birth child, Corrin, as his new sibling. However, Ryoma lost this sibling when they were kidnapped as an infant and raised in Nohr. In line with his position as the direct successor to the helm of Hoshido, Ryoma is a valiant warrior and leader. He has spent years honing his edge in battle and developing a keen mind to better honor his father's legacy. He cuts a figure of calm collectedness, keenly scrupulous as he rigorously analyzes the innumerable situations that he finds himself mired in before finalizing any decisions. This greatly contributes to this aura of charisma and wisdom that he is known to exude, one that sees many turning to him for his sagely advice in support conversations. Adept in the art of war, this, combined with his shrewd sense of insight and intelligence, has helped Ryoma to lead the Hoshidan army to victory in the campaigns they have participated in. Further complementing his astute skill as a battle tactician is that of his skill with the sword, one that is regarded to be unparalleled throughout the kingdom of Hoshido.

Ryoma is both an admired figure by his people and his siblings. Despite his many duties, he is keenly aware of his siblings strengths and weaknesses, including both Corrin and Azura. With the former, he provides wise council throughout the war and is pleased with Corrin's growth throughout their journey. Though Azura pushes her self away from Ryoma and the others once Corrin returns, Ryoma is left hurt by it and tells her that despite Corrin's return, Azura still remains his sister in his eyes and encourages her to open up to him and their siblings. He has brown hair, brown eyes and wear red armor.