Ryuboshi is the second son of King Neptune and Queen Otohime, a prince of the Ryugu Kingdom. As an oarfish merman, he has an extremely tall, thin physique, wide eyes, long wavy dark pink hair, and distinctive beaver-like teeth. His purple tail features white polka dots and a red fin. He typically wears a fancy robe-like garment with puffed sleeves at the shoulders and wrists, secured by an orange sash holding his two swords; during the Levely, he wore a light-colored shirt. His personality is upbeat and jovial, often ending sentences with musical scales like "so-la-ti-do." This habit began in childhood to cheer his younger sister Shirahoshi after their mother's death, preventing her emotional distress from triggering her latent ability to summon Sea Kings. Despite his cheerfulness, he turns serious when confronting threats to his family or kingdom. Alongside brothers Fukaboshi and Manboshi, he exhibits a strong protective instinct toward Shirahoshi, fulfilling their mother's final request. As one of the three princes, Ryuboshi holds royal authority and ranks among the Neptune Army's most powerful warriors. He specializes in dual-wielding long rapiers using the Merman Gujutsu swordsmanship style. He and his brothers collectively defeated drug-enhanced sea beasts that overwhelmed the army, showcasing their elite status. However, New Fish-Man Pirates officers using Energy Steroids later captured them. His fighting skills proved instrumental in the battle against Hody Jones' forces at Gyoncorde Plaza. His background includes witnessing Queen Otohime's assassination. When Shirahoshi nearly cried in grief—risking a catastrophic Sea King summoning—Ryuboshi and Manboshi immediately sang and danced to distract her, suppressing their sorrow to honor their mother's dying wish for peace. This solidified his commitment to Shirahoshi's well-being. During the Fish-Man Island Arc, he retrieved the Straw Hat Pirates to relay Jinbe's message, expressed concern over Madam Shyarly's prophecy, fought to rescue King Neptune from execution, aided Shirahoshi in evading Vander Decken IX's attacks, and helped contain the Noah crisis. At the Levely Arc, Ryuboshi accompanied his family to the Reverie at Mariejois. He encouraged Shirahoshi's fascination with the surface world while cautioning her against openly mentioning Monkey D. Luffy. When Saint Charlos attempted to enslave Shirahoshi, he supported Fukaboshi's defensive stance and stood by Neptune during Saint Mjosgard's intervention. His character reflects consistent dedication to family duty and his mother's ideals of human-fish-man reconciliation. This is evident in defending Fish-Man Island during Hody's coup and his diplomatic presence advocating peaceful coexistence at the Reverie.