In Spirited Away, the boy who turns into a dragon is Haku.
Haku first appears as a mysterious boy who helps Chihiro navigate the spirit world and find work in Yubaba’s bathhouse. Later, Chihiro sees a dragon being attacked by paper spirits and realizes that the wounded creature is Haku. His dragon form reflects his identity as a river spirit rather than a human boy.
Haku has forgotten his true name because Yubaba controls him by taking it. Near the end of the film, Chihiro remembers falling into the Kohaku River as a child and recognizes Haku as the river’s spirit. His full spirit name is Nigihayami Kohakunushi, while Haku is the name used throughout most of the story.
A common mix-up is confusing Haku with Kamaji, the boiler-room worker, or No-Face, the silent spirit. Chihiro is the film’s human protagonist; Haku is her supernatural ally and the character who transforms into a dragon.