My younger sister is at an age where she's worried about her figure, so she started working out at home to lose weight! Despite her best efforts at restricting her diet and exercising, she's stressed out by the sudden diet and is frustrated every day. However, the clothes she wears while dieting are designed for ease of movement and are very sexy! I hadn't noticed before, but my sister's breasts are surprisingly big, and they're shaking all over the place! What's more, when I look closely, her nipples are visible through her sweat! Seeing her like that, I get an erection and my sister finds out, but she grabs my dick to relieve stress!