Arisa, a devout and innocent girl, is haunted by dreams of her brother, Souta, in ways that make her blush. She struggles to suppress these thoughts, knowing they're wrong, yet her body betrays her, aching for something she doesn't understand. One day, she finds a hidden compartment in her room, containing a collection of erotic art and a vibrator. Her curiosity piqued, she tentatively touches herself, gasping as waves of pleasure course through her. As she loses herself in her newfound pleasure, she imagines Souta's hands on her body, his lips on hers, leading her deeper into her taboo fantasies.