Lord Uroko is a key figure in the world of the anime, existing as a scale of the Sea God and serving as the protector and spiritual guide of the underwater village of Shioshishio. He is addressed with the honorific Uroko-sama and is treated with deep respect by the sea people, though he clarifies that he is not a deity himself but merely a scale that once sat on the Sea God's shoulder blade. His physical appearance shows noticeable blue-green shimmering scales on his upper arms and chest, and he possesses the ability to breathe underwater, his Ena being more visible than that of ordinary sea dwellers. He is often depicted with long gray hair and blue eyes, and his form can be compared to a serpentine creature when coiled in meditation.

Uroko's personality is layered and often contradictory. On the surface, he presents a playful, unpredictable, and sometimes lecherous demeanor, frequently drinking sake and making risqué remarks, which makes it difficult for others to take him seriously. He can be sarcastic and condescending, especially toward those he considers naive, and he sometimes curses others for his own amusement. Beneath this façade, however, he is a deeply knowledgeable and insightful being. He possesses a profound understanding of the world's ancient laws and the consequences of the characters' actions, often serving as a voice of reason and a moral compass. He is guided by a sense of duty to maintain the traditions of the sea, yet he is not rigid; he is capable of change and growth.

His motivations stem from his role as a scale of the Sea God. He carries the sacred fire, a literal and metaphorical warmth that prevents the sea from freezing and sustains the village. He shares this fire with the villagers for ceremonies, funerals, and everyday warmth. At first, Uroko harbors a strong hatred for people from the surface, viewing them as separate and inferior. However, through witnessing the relationships between land dwellers and sea dwellers, particularly the marriage of Akari Sakishima to a surface man, he gradually comes to understand that there is no essential difference between the two groups. This realization prompts him to break the very traditions he is meant to uphold, choosing to let human emotion and connection guide his decisions rather than blind adherence to divine will.

Uroko's role in the story is multifaceted. He acts as the guardian of the sea village and its rituals, overseeing important ceremonies such as the Ofunehiki. He also functions as a source of wisdom and cryptic warnings, often hinting at the larger cosmic forces at play, including the waning power of the Sea God due to lost love. He supports the main characters during critical moments, providing spiritual fire, guidance, and at times, tough counsel. He is also a tragic witness to the cycle of sacrifice and heartbreak that has repeated for generations. His personal history includes unrequited feelings for the Princess, Ojoshi-sama, whom he loved but could never touch or speak with because of his nature as a scale. This lingering affection shapes his understanding of love and loss.

Key relationships include his interactions with Hikari Sakishima, whose stubbornness and sense of responsibility Uroko recognizes and gently guides. He also has a complex connection to the village elders and the younger generation, often caught between enforcing the old ways and allowing change. His bond with the Sea God is the most fundamental, as he feels the God's emotional state and the resulting environmental crises. He also shares a notable connection with the character Ojoshi-sama, his past love, whose story influences his later decisions.

Over the course of the narrative, Uroko undergoes significant development. He begins as a detached, hedonistic figure who seems to prioritize his own amusement and the rule of law. As the story progresses, his actions reveal a deeper compassion and a willingness to let humanity forge its own path. He stops interfering in the final Ofunehiki, effectively abdicating his role as an enforcer of divine law and allowing the characters to decide their fate. His final curse on the village is understood as a desperate attempt to preserve a dying culture, but by the end, he accepts that the old world must give way to one governed by human emotion.

Uroko's notable abilities include providing and controlling the sacred fire, which is essential for the survival of the underwater village during the cold period. He can amplify the fire's warmth and use it in various rituals. As a scale of the Sea God, he possesses a heightened Ena, granting him enhanced underwater abilities and a visible scale armor. He is also a keeper of ancient knowledge and can perceive the emotional state of the Sea God, allowing him to foresee impending disasters. His presence alone carries authority, and his words are often heeded by the village elders. Despite his mischievous nature, his powers and wisdom make him one of the most consequential figures in the story.