My niece came to Tokyo for a club activity trip and ended up staying at my house for a while. It had been a while since I'd seen her, and it turned out she'd grown into a fine female athlete, apparently on the university's track and field team. Being a self-proclaimed track and field enthusiast, I asked her to show me her running form. Watching my niece run seriously on the treadmill, drenched in sweat, her pheromones made my dick twitch! I couldn't resist her sweaty, big butt...