Nagisa Shirai is a young boy who appears in the second season of the anime and in the manga. He is characterized by his short blue hair and gray eyes, and he is two years younger than the mermaid princess Hanon Hosho. His background is that of an ordinary human boy with no connection to the magical or underwater worlds, which makes his role distinct from the central mermaid protagonists. He first meets Hanon after retrieving a piece of sheet music for her, an act that sparks his immediate and strong infatuation. His personality is marked by a persistent, almost relentless determination to win Hanon’s affection. In the manga, he is depicted as candid and childlike, while in the anime he retains a similar earnestness but also displays a more playful and sometimes short-tempered side. Despite his lack of special talents or magical abilities, he constantly strives to make Hanon laugh and to prove the depth of his feelings. His primary motivation is his love for Hanon, and he is willing to go to great lengths, even putting himself in danger, to protect her and earn her regard. His role in the story is that of a supportive love interest and a source of comic relief, but he also serves as a catalyst for Hanon’s emotional growth. The central relationship in his life is his pursuit of Hanon, who initially dismisses him because of her infatuation with an older man, Tarō Mitsuki. This creates a one-sided dynamic that gradually evolves as Nagisa’s sincerity and persistence wear down Hanon’s resistance. His rivalry with Mitsuki, whom he views as a more talented and mature figure, drives much of his character development. Over the course of the manga, Nagisa matures from a clumsy admirer into a more confident and considerate partner. A key turning point occurs when he confesses his love at the beach and selflessly offers to let Hanon go if she still loves Mitsuki, a display of emotional maturity that moves Hanon to tears and leads her to reciprocate his feelings. By the end of the manga, Nagisa and Hanon are in a committed relationship, though Hanon’s eventual need to return to the ocean remains an unresolved tension. He possesses no magical abilities, but his notable trait is his emotional resilience and unwavering devotion. His lack of powers is explicitly contrasted with Mitsuki’s musical talent, emphasizing that his love is grounded in effort and sincerity rather than innate gifts.