Nagiinyo is a spirit dispatched by Princess Grace to monitor and assist Princesses Fine and Rein in safeguarding the Wonder Planet. He possesses green hair and green eyes. His attire displays symbols representing each kingdom of the planet, signifying his connection to the entire realm. His most distinctive possession is a harp, which he consistently mistakes for a violin. He employs this instrument to entertain and spread cheer, aligning with the princesses' objective on a smaller scale. While Fine and Rein occasionally find his musical performances bothersome, the lyrics of his songs convey truthful insights about ongoing situations.

Initially appearing sporadically as a wandering minstrel who charmed ladies with his melodies, it is later revealed his presence and musical interludes served a deliberate purpose; he was acting under Princess Grace's directive as her messenger all along. As the series progresses, Nagiinyo becomes the object of romantic affection for Camelot, one of the princesses' maids. It is suggested he may have harbored romantic feelings for Princess Grace in the past, indicating a personal history tied to the legendary figure.