My older sister is a cheerleader, but in reality she has massive 103cm "I-cup" breasts, drawing constant attention from those around her. As her striking figure becomes more noticeable, her friends grow increasingly fascinated—soon seeing her as an object of their sexual desires. Some sneak into the bathroom to grope her big tits, while others take chances to fondle her body during practice breaks. Amidst it all, the protagonist also finds himself irresistibly drawn to her, struggling to suppress his overwhelming feelings.