TV-Series
Description
Shion Sonozaki is the identical twin sister of Mion Sonozaki, born on July 10, 1968. Originally designated as the elder twin and named "Mion," she swapped identities with her sister during the ceremony choosing the Sonozaki family heir. Consequently, her younger sister received the demon tattoo marking the successor, and Shion took the role of the younger twin. This reversal led to her being sent to the strict St. Lucia's boarding school, which she despised. She escaped in 1982 with help from Sonozaki bodyguard Tatsuyoshi Kasai, relocating to Okinomiya under her family's condition of discretion.

Physically resembling Mion with long mint-green hair and turquoise eyes, Shion typically wears her hair in a half-ponytail secured with a yellow ribbon. Her attire includes a school uniform of a short-sleeved white shirt, striped ribbon, and navy blue miniskirt, or casual outfits like a sleeveless striped turtleneck and black miniskirt. She also wears the Angel Mort waitress uniform while working. Her primary weapon is a stun gun, though she shows proficiency with firearms in certain situations.

Shion's personality blends surface refinement with underlying shrewdness, impulsivity, and manipulative tendencies. Her time at St. Lucia fostered rebellion, and she exhibits strong protective instincts towards those she cares about. However, she is prone to jealousy and envy, particularly regarding Mion's status as heir and Rika Furude's revered position. This jealousy worsens under Hinamizawa Syndrome, a parasitic infection affecting brain function. Her prolonged absence from Hinamizawa during childhood increased her susceptibility. Symptoms include severe paranoia, auditory hallucinations, and violent behavior.

Her relationship with Hōjō Satoshi defines her. She fell deeply in love after he defended her from delinquents, believing he embodied warmth and heroism. She supported his efforts to buy a stuffed bear for Satoko's birthday by convincing the store owner to hold it. Following Satoshi's disappearance after the 1982 Watanagashi Festival, Shion's mental state deteriorated. In the "Meakashi-hen" arc, afflicted by advanced Hinamizawa Syndrome (Stage L5), she blamed Satoko for Satoshi's suffering and orchestrated murders targeting individuals she held responsible, including village elders and family members. This culminated in her kidnapping and torturing Satoko before committing suicide.

Conversely, in arcs like "Minagoroshi-hen" and "Matsuribayashi-hen," Shion honors Satoshi's request to protect Satoko, forming a sisterly bond. She becomes fiercely defensive, threatening to kill Satoko's abusive uncle, Hōjō Teppei, and even offering her life to Takano Miyo for Satoko's safety. During the Yamainu siege, she prioritizes non-lethal tactics, using her stun gun to incapacitate attackers. This reflects her capacity for growth, learning to control volatile emotions and channel protectiveness constructively, contrasting her earlier violent descent.

In the "Cotton-Revealing" arc of "SOTSU," Shion's interactions with Keiichi Maebara inadvertently trigger Mion's jealousy. After Keiichi gifts the festival prize doll to Mion, Mion adopts Shion's persona to express her feelings. When the real Shion interacts casually with Keiichi during the festival, Mion's paranoia escalates into Stage L5, fueled by Satoko's manipulations. Shion, traumatized by prior experiences like Sonozaki fingernail torture, fears for Keiichi's safety and suspects family involvement in curse-related deaths. A confrontation at the Sonozaki mansion sees Mion, delusional, subdue Shion with a taser and strangle her, believing this ends the violence. Mion briefly regains clarity and grieves, but the Syndrome resurfaces, leading her to confront Oryou.

Shion's relationship with Mion is complex, marked by affection and tension from their swapped identities and Mion's role as heir. They frequently impersonate each other, maintaining the swapped identities. Despite closeness, Shion harbors resentment over Mion's privileged position, while Mion's duty sometimes leads her to enforce family discipline against Shion, as seen in her participation in Shion's fingernail removal punishment. Shion also interacts with others like Kasai, her guardian and source of unsettling stories causing her to hate canned food, and Keiichi, whom she views as a potential replacement for Satoshi but finds immature.

In the "Rei" manga, set 35 years after the main events, Shion marries Satoshi, though details of their life together are sparse. This represents a positive resolution beyond the central tragedies.