Hakuryū protects the parallel world of Kyō, mirroring Heian-period Kyoto, as the White Dragon God. His powers weaken drastically when the Taira clan releases disruptive onryō, vengeful spirits terrorizing the land. This depletion forces him into a human form resembling a 10-year-old boy, approximately 130 cm tall, with cyan waist-length hair and amber eyes. Trapped in this diminished state, he cannot return to his true dragon form. He initially appears to Nozomi Kasuga and her friends at their high school, inadvertently transporting them to Kyō while seeking aid. He deeply longs for Nozomi's trust but is saddened by his inability to protect her as the Priestess of the White Dragon, the only one capable of sealing the onryō.

Hakuryū's bond with Nozomi evolves. He occasionally regains sufficient power to temporarily assume an adult human form, standing 185 cm tall while retaining his cyan hair and amber eyes; his core personality remains consistent with his child form. In the sequel *Unmei no Labyrinth*, his weakened state prevents him from transporting Nozomi back to Kyō when a magically constructed labyrinth emerges, contributing to her memory loss. His recovery and stability become integral to resolving this threat, requiring the characters to restore his strength to dismantle the labyrinth.

He maintains protective bonds with key figures, particularly Ridvan (Chi no Genbu), who acts as his and Nozomi's mentor and is affectionately called "Rid-sensei" by the guardians. His interactions reflect gentle yet occasionally stern guidance, emphasizing their shared goal of stabilizing Kyō. In later narrative expansions, such as a Christmas event in *Unmei no Labyrinth*, Hakuryū's restored presence aids the group in confronting arcane threats, reinforcing his role as a linchpin in maintaining balance between the worlds.