One day, while commuting and going to school with my suddenly appeared sister-in-law, we found ourselves in an overcrowded train and bus with a 120% occupancy rate, in an extremely close state with her! Unable to move, I stayed still and was suddenly aroused by the scent of her hair, the feeling of her butt, and the sight of her cleavage! Moreover, pushed from all sides, my erect penis slipped into my sister-in-law's crotch, resulting in a forced open-leg state! 'This is bad!' I thought, but the excited sister-in-law took out my penis from her pants and invited me, 'If it's just rubbing, it's okay to do it raw.'