Boris languishes in captivity on Wild Island, imprisoned by animals led by the gorilla Saiwa who exploit his unique ability to temporarily lift the sinking island. This captivity interrupts his intended rite of passage, a journey to transform into a mature "After Dragon" capable of fire-breathing and greater strength.

Physically, Boris resembles a traditional Western dragon, marked by bright colors, surprisingly tiny wings, and long ears. His elephantine bulk contrasts with his inability to breathe fire at his story's beginning. Though approximately ten years old in dragon years—equivalent to one hundred human years—he remains very young for his kind.

Personality-wise, Boris presents a cheerful, playful front, often providing comic relief. Yet he harbors significant fears, particularly a profound cowardice regarding fire and large bodies of water. These fears, coupled with low self-confidence, initially cripple his potential. His relationship with Elmer begins with distrust, as Elmer sees him as a solution to personal problems, but evolves into genuine friendship built on mutual reliance and compassion. Boris deeply admires his older brother Horacio as a role model.

A crippling wing injury sustained during his escape with Elmer grounds him for much of their journey, amplifying his existing fears and insecurities. Despite these burdens, Boris transforms when confrontation demands courage. He spontaneously conquers his terror of fire to save Wild Island, unleashing his first fiery breath and completing his rite of passage. This ascension to After Dragon grants him full flight capability while altering his appearance minimally. His newfound courage and self-assurance culminate in sending Elmer away to independently face his own destiny.