Hanyuu, revered in Hinamizawa as the deity Oyashiro-sama, is Rika Furude's ancestor. She appears as a young girl with purple eyes, long light purple hair, and dark purple horns—one cracked—sprouting from her head. Her attire alternates between traditional shrine maiden garb with a red bow and light red sleeves and a school uniform of light blue vest, white shirt, and red skirt when posing as a transfer student.

Over a millennium ago, she arrived at Onigafuchi Swamp—later Hinamizawa—as the demon goddess Hai-Ryūn Ieasomūru Jeda. Seeking coexistence with humans, she faced discrimination for her horns. She married Furude Shrine heir Riku, bearing their daughter Ouka. The merging of demon and human bloodlines birthed Hinamizawa Syndrome, causing advanced sufferers to acutely sense her presence. To end conflict, Hanyuu allowed Ouka to sacrifice her with the sword Onigari-no-ryuuou, an event initiating the Watanagashi Festival and cracking one horn. Her death rendered her incorporeal and unable to interact with humans until Rika's birth centuries later.

Hanyuu acts as Rika's guardian and mother figure, teaching skills like cooking. Their linked senses allow shared physical experiences. She grants Rika time-looping powers upon death, though Rika retains fragmented memories due to the cracked horn. Hanyuu shifts between human and incorporeal forms, wields divine abilities like time-stopping, teleportation, flight, mind control, and adversary-weakening. She occasionally cures Hinamizawa Syndrome, but effects fade if patients leave the village.

Timid and pessimistic, Hanyuu often mutters "au au" when distressed and excessively apologizes. She resents villagers' worship and sacrifices under her Oyashiro-sama identity, sometimes throwing tantrums. Despite her gentleness, she becomes stern and manipulative to intimidate foes or persuade allies. Deeply devoted to Rika, she remains through endless loops, tempering Rika's optimism to shield her from disappointment.

In *Higurashi Gou* and *Sotsu*, Hanyuu's powers wane dramatically. She reveals her weakened state stems from being a "failure" and fragment of Eua, a higher entity calling herself the "original." As her abilities fade, she warns Rika of Onigari-no-ryuuou's power to permanently kill loopers—misinterpreted by Rika as suicide advice. Hanyuu vanishes after expending her energy, leaving Rika alone in new loops. Later, in *Kagurashi*, she reappears in the Sea of Fragments, draws power from fragments, and uses Onigari-no-ryuuou to defeat Eua, damaging her horn.

Guilt and protectiveness define Hanyuu's ties to others. She silently follows and apologizes to Hinamizawa Syndrome victims, inadvertently worsening their paranoia and causing the footsteps and voices they hear. Rena Ryuugu occasionally senses her due to spiritual sensitivity; Hanyuu once halted Rena's suicide. She aids allies like Detective Ooishi through reassurance and subtle manipulation.