The character known in Western localizations as Fly is the protagonist of the story, originally named Dai. He is a young boy, approximately twelve years old at the start of the adventure, who was found as a baby on a small boat that drifted ashore on the southern island of Delmurin. He was discovered and raised by Brass, an elderly monster magician who became his adoptive grandfather, making Fly the only human inhabitant on an island populated entirely by monsters who live in peace.

Fly grows up with a pure and energetic spirit, harboring a powerful dream of becoming a great hero. He has a strong sense of justice and a deep loyalty to his family and friends, often displaying a naivety about the wider world due to his isolated upbringing. While Brass attempts to train him as a magician, Fly shows little talent or interest in magic, preferring physical combat and swordsmanship. Despite his cheerful disposition, he is prone to recklessness and stubbornness when protecting others, and he has a mischievous side that emerges in quieter moments.

His life changes dramatically when the Dark Lord Hadlar is resurrected by a greater evil, threatening the world once more. The legendary hero Avan arrives on Delmurin to train Fly and another student named Pop. This training is cut short when Hadlar attacks, forcing Avan to sacrifice himself to save his disciples. Witnessing the death of his beloved master becomes Flys primary motivation, spurring him to leave his home alongside Pop to avenge Avan and fight against the forces of evil.

Fly is not an ordinary human. In moments of extreme danger or rage, a mark known as the Dragon Crest or Emblem of the Dragon appears on his forehead. This crest dramatically enhances his physical abilities, granting him immense strength and resilience. It is later revealed that this power is his inheritance as the son of Baran, the formidable Dragon Knight, and a human princess. Flys real name, given by his birth parents, was Dino. This heritage places him at the center of the conflict, though he initially knows nothing of his origins.

Throughout his journey, Fly forms deep and meaningful bonds with his companions. His closest friend is Pop, a cowardly but intelligent magician who acts as his foil and eventual brother in arms. Together they meet Maam, a disciple of Avan who fights with a magic gun and later as a martial artist, and Princess Leona of Papunica, a sage-in-training who becomes a trusted ally. Fly also clashes with and eventually wins over powerful enemies, including the beast general Crocodine and the dark warrior Hyunckel, turning them into valuable friends. He maintains a deep admiration for his fallen master Avan and a loving, if sometimes exasperated, respect for his grandfather Brass.

Fly begins as a boy with raw potential but little control over his abilities. Through rigorous training and countless battles, he matures into a warrior of great skill. He masters the Avan Style Sword Techniques, which include powerful attacks such as the Earth Slash, which focuses his strength, and the Air Slash, which cuts through the air itself. As he learns to accept his heritage as a Dragon Knight, he gains the ability to consciously control the power of the Dragon Crest, unlocking even greater forms and attacks that are essential to defeating the Demon Lords army. He also develops from a child acting on pure emotion into a determined hero who carries the hopes of the world on his shoulders. In many international releases of the original anime, his name was changed to Fly to avoid the homophone of the English word die.