O-Nao, youngest daughter of Tetsuzo Hokusai from his first marriage, lives apart from her father with her mother, her blindness and fragile health deepening his avoidance. Shut out from his artistic pursuits, she endures emotional neglect as Hokusai withdraws from her disability and illness. Her bond with half-sister O-Ei becomes her lifeline: through guided boat rides where ripples and birdcalls replace vistas, snowy walks where silence sharpens her senses, and shared encounters with petals or flowing streams, O-Ei translates the visible world into textures and sounds.

As O-Nao’s health declines, O-Ei coaxes Hokusai to her bedside. He paints a guardian deity over her—a fleeting gesture of care—but cannot forestall her death. A sudden wind sweeps through his studio afterward, scattering a tsubaki flower O-Ei once gave her, its presence echoing impermanence and Hokusai’s unresolved guilt.

O-Nao’s brief attempts to bridge the distance—reaching toward her father’s face, her unseeing gaze unsettling him—reveal his fear of vulnerability beyond art’s control. Her existence underscores O-Ei’s empathy against their father’s detachment, framing disability as both isolation and insight in Edo-era Japan. Though fictional, her narrative weaves absence into thematic texture: her death lingers as unresolved sorrow for O-Ei, a quiet counterpoint to Hokusai’s legacy, her unseen perspective amplifying contrasts between artistic immortality and fragile, embodied truth.