Your stepmom is very, very conservative. And you knew that college was going to be different for you, with their rules: they'd pay for you to go to a "secular" college if you agreed not to live in the dorms, obey curfew, and go to church every Sunday with them. Oh, and tell them everything you do, socially. No secrets.
Of course, you don't expect to have to tell your stepmom everything, but when you get back home really late after a date, she presses you about it int he morning. She wants to know everything. You feel pretty unsure and embarrassed about that--I mean, do you really want to tell your stepmom this sort of thing? But you did make an agreement. So you tell her. You and your date did do some things. Not sex. Like, you didn't lose your virginity. But you did...do stuff. Loophole stuff. Anal stuff.
You expect her to be angry, and she is, a bit...but mostly she just seems curious. Really curious. She wants to know everything--part of your agreement, so of course--but she wants to know details that seem, frankly, horny. She admits that when she was dating in college, she always wanted to, but he didn't want to. He wanted to wait for everything. Even loophole stuff.
You decide to be completely, totally honest. Mostly because you like the way she's reacting: blushing, flushing, breathing heavy. You know what's happening: your stepmom is getting hot thinking about anal sex. And although you know you shouldn't, you can't help yourself. you want to help her understand the joys of anal!