"Did you have such a big boob...?" My younger sister has sweaty nipples on a diet! My younger sister suddenly started exercising at home to lose weight recently. My younger sister is desperately trying to go on a diet but is stressed out by dietary restrictions and exercise, and honestly, I don't like it. However, while on a diet, she is quite sexy and her big breasts are shaking all the time. What's more, when I looked closely, my nipples were visible through sweat! I saw that, but I got an erection even though I was a little sister...