Kaya is a young girl born with branches and leaves growing permanently from her head. With age, her body and mind experience recurring abnormalities, including physical transformations and psychological disturbances linked to supernatural entities. She disappears into a mountain forest during a storm while with her older brother, Yoshirou, who searches for her for years.

Ginko encounters Kaya in the mountains, observing branches and leaves protruding from her body. He identifies her as the mountain lord, an unusual role for a human. Her duties involve maintaining the mountain's natural balance and guarding its spiritual essence. She retains fragmented memories of her human life, especially her bond with Yoshirou. Ginko informs Yoshirou of Kaya's presence, rekindling his hope for reunification. Ginko facilitates contact, leading to an emotional reunion between the siblings. However, this reunion triggers severe consequences due to the mountain's profound spiritual bond with Kaya. Her struggle intensifies as she faces an irreconcilable conflict: continuing her role as mountain lord to preserve the ecosystem or returning to her human family. The mountain's fateful connection exerts powerful influence, making abandonment of her duties potentially catastrophic for both realms.

Kaya's physical form becomes increasingly intertwined with the mountain's flora, symbolizing her deepening assimilation into its spiritual fabric. The narrative centers on her internal conflict and the external repercussions of her dual existence as both human and nature guardian.