A brother and sister who grew up receiving ample love from their parents were always together, no matter what. As the brother approached adulthood, his penis significantly grew, and the sister developed a large, rounded buttocks that didn't match her slender figure. Along with these physical changes, their emotional states also shifted. The brother's affection for his sister began to focus on her rounded buttocks. The sister also sensed her brother's changes and started to feel something beyond sibling love towards him. Unaware that her buttocks were the target... This problematic work depicts the abnormal love between a brother who favors buttocks and a sister who accepts it, in three parts.
