Hanyū Furude embodies the true form of Oyashiro-sama, initially manifesting as a spiritual entity tied to Hinamizawa village. She possesses the appearance of a young girl with purple hair, violet eyes, and dark purple horns, one of which is cracked. Her manifestations take two primary forms: a translucent spirit clad in shrine maiden attire and a visible human form attending school. She frequently utters "auu" and refers to herself using the pronoun "boku".

Her origins stretch back over a millennium as the demon goddess Hai-Ryūn Ieasomūru Jeda, who led her clan to the Onigafuchi Swamp, later known as Hinamizawa. Facing discrimination due to her horns, she eventually won the love of Furude Riku, heir to the Furude Shrine. Their union produced a daughter, Furude Ōka, integrating demon blood into the human lineage and potentially initiating Hinamizawa Syndrome. To quell rising villager paranoia, Hanyū accepted blame for societal sins. Sacrificed during the first Watanagashi ceremony, Ōka executed her using the sword Onigari-no-ryuuou, cracking her horn. Posthumously revered as Oyashiro-sama, her death spawned the legend of the village curse.

After death, Hanyū existed as an incorporeal spirit, observing Hinamizawa unseen until the birth of her descendant, Furude Rika. Rika became the first person in centuries to perceive her. Hanyū served as a guardian and maternal figure, teaching Rika essential skills. Their senses remained linked, allowing Hanyū to experience Rika's physical sensations. She gained the ability to traverse the Sea of Fragments, enabling Rika's time loops upon death to evade fate. Her powers waned over cycles, restricting loop resets to two weeks prior to Rika's demise. The cracked horn contributed to Rika's fragmented memories between fragments.

Typically timid and pessimistic, Hanyū frequently apologizes to those afflicted by Hinamizawa Syndrome, whose paranoia misinterprets her presence as ominous footsteps or voices. When angered or invoking divine powers, her pupils glow red and her voice shifts to a stern, mature tone. She employs this "demonic voice" during confrontations, such as intimidating the Yamainu paramilitary group or addressing Miyo Takano as a "child of man" to emphasize their species divide. Despite her gentle nature, she demonstrates strategic manipulation, using her appearance to persuade Detective Ōishi.

In Higurashi GOU and SOTSU, the entity Eua identifies Hanyū as a "failure" and "part of herself," with audio commentary confirming Hanyū formed from a fragment of Eua after damage to Eua's horn. Hanyū's powers diminish significantly early in GOU; she appears only briefly as a fading spirit to warn Rika of another looper's interference before vanishing. This departure isolates Rika in subsequent loops. Hanyū later reappears in Kagurashi-hen, wielding the Onigari-no-ryuuou against Eua after empowering herself with fragmented realities.

Her relationship with Rika is central, blending maternal protectiveness with deep companionship. Hanyū expresses willingness to endure endless loops solely to remain with Rika. This bond strains under Rika's frustration during cyclical tragedies, yet Hanyū consistently prioritizes Rika's wellbeing, even intervening physically to prevent misuse of god powers. The sensory link leads Rika to torment her with spicy food. Hanyū also shares connections with other characters: Rena Ryūgū senses her spiritually, potentially linking to Rena's past suicide attempt, and Ōishi briefly interacts with her during a critical consultation.

Hanyū's abilities extend beyond time manipulation. She can stop time, teleport, fly, perform mind control, and temporarily suppress Hinamizawa Syndrome. In her goddess form, she exhibits superhuman strength, weakening Takano when empowered by Tamurahime no Mikoto. Her combat proficiency emerges in Kagurashi-hen, showcasing advanced swordsmanship with the Onigari-no-ryuuou.