So, her older sister told me she's been keeping me on a no-masturbation streak while she's away... She said it must be tough for a guy to hold back, so I offered to help her out with a little blowjob. But she warned me not to cum too quickly. She said she'd be back soon, so I promised to manage her boyfriend's ejaculation until then. But her little sister is such a little devil, she's driving me crazy with her teasing and making me cum all over the place, even though I'm supposed to be resisting!