Disclaimer: All recognizable characters and elements from the Ayashi no Ceres/Ceres Celestial Legend manga belong to Yuu Watase. No copyright infringement is intended.
This is not her brother. This is not Aki. Aki's eyes were warm, not heated. Her brother had never looked at her like this.
"I see you in there, Ceres," the Progenitor says. "Come out."
Aya can feel Ceres inside her, full of rage. Ceres wants to come out, but Aya can't let that happen. This boy – man – is not her brother but he's using her brother's body and Ceres will tear it apart if she's released. Aya imagines Aki as bloody chunks of meat the way she's seen others and it's worse than having his hands caress her body.
Aki is still in there somewhere. No matter what the Progenitor says, Aya believes her brother is still there and his body will be his own again one day. But now there's only the man who once stole Ceres's hagoromo and forced her to be his wife. He uses her brother's hands to unbutton her blouse, to squeeze and pinch her breasts. Aya has to fight Ceres to keep her from seizing control of her body.
"You are my woman," the Progenitor says. He turns her around and pulls her flush against the front of his body. He's excited, Aya can feel it pressing against her. He slips his hand under her skirt and into her panties.
No. She wants Toya to be the first. Aya tries to struggle but her twin is stronger than he looks and his hold on her doesn't relent. She's only succeeding in rubbing her butt against him so she stops. His fingers stroke her until her body doesn't want it to stop. Aya hates it. This is an evil man using her poor, innocent brother's body to molest her and Ceres is screaming for his blood, and she can't help that the Progenitor is so skilled she's wet.
"Ceres," he whispers into her ear. He nuzzles her neck and then bites down, leaving his mark on her skin. Aya gasps and he pushes a single finger inside her.
Then he withdraws it and sticks it into his mouth and releases her. "You are still mine, forever."
Aya listens to his footsteps as he walks away. She should be relieved. She is relieved. It's just that this need between her thighs is purely physical like an itch and it hasn't been scratched to satisfaction. Her hands are shaky when she fixes her clothes.
The nurse believes her when Aya says she's not feeling well. She lies down in the nurse's office behind a screen and waits for the feeling to go away. Ceres is quiet. Aya slides her hand between her legs and thinks of Toya.