Senko Himemiya, later Chika Midarezaki, emerged from the Himemiya clan—a lineage notorious as the "House of Oni." Bound by the brutal tradition of the "Solitary Doll," the family’s youngest member became a vessel for collective anguish. Senko endured this role until her sister, Reiko Himemiya (later Yūka Midarezaki), inherited the torment. Senko then mirrored her abusers, orchestrating Reiko’s physical and psychological suffering through bribed classmates. The cycle fractured when Reiko fled, exposing Senko to the abuse she once wielded, unraveling her psyche.

Her path collided with Ginichi Kizakura (later Ginka Midarezaki), an ex-yakuza who once vowed her sanctuary. Desperation drove her to claim his promise, but Ginka’s embrace of a feminine identity strained their reunion. Kyōka Midarezaki, the family’s shrewd matriarch, intervened, fabricating a DNA test to anoint Senko as a "Child of Enka"—a ruse to rebrand her as Chika Midarezaki and sever her from the Himemiya curse.

As Chika, she cloaked lingering guilt behind apathy, secretly safeguarding her newfound family and allies. Her fixation on Ginka—pushing him to reclaim his past identity—betrayed an unyielding grip on their history, sparking unresolved romantic friction. Beyond familial ties, she forged bonds with schoolmates Momo, Shizu, and Hi, masking protectiveness with detachment. Yūka’s gradual forgiveness and Kyōka’s guidance nudged Chika toward confronting her trauma, though her sharp edges endured. Her journey closed not with resolution, but fragile steps toward peace—a quiet defiance of the shadows that shaped her.