Nao Takanashi, a second-year middle school student, harbors intense feelings for her older brother Shuusuke, bordering on a brother complex. Eager to be viewed as a woman by him, Nao constantly flirts with Shuusuke, who reciprocates and even encourages her advances. Their dynamic shifts when Nao stumbles upon a photo album from their childhood that excludes her. This revelation deepens Nao's affection for Shuusuke, but soon her desire to monopolize his attention faces unexpected challenges.