As incest gains attention, the younger sister begins developing curiosity about sex and becomes increasingly interested in her brother's body as a close family member. She notices the physical differences between boys and girls and grows intensely curious about the "penis" she doesn't have. Used to bathing together with her brother, she unconsciously asks boldly, "Onii-chan, can I touch and look at your dick?" urging forbidden sibling intercourse. Her growing awareness and actions reveal her emotional development and transformation.