I began to regularly service Mrs. M. with my mouth, kneeling. There was no question of me penetrating her.
"You'd just come right away. Little dicked guys like you always do. But I'm going to help you. I'm going to get you used to being with a woman, then you won't be so overexcited." So she let me go down on her, and after she was finished--she would usually wipe her cunt on my face when she was done--I was allowed to jerk off wearing a rubber while I looked at her pussy.
After a week of this, she had the idea that I should kiss her asshole when I jerked off wearing the rubber. She was on her back, with her legs up: that way I had my nose in her pussy, and could enjoy its wonderful smell, while my mouth was on her ass. She didn't want me "bothering" her cunt after she came, but she did like me softly kissing her asshole. It was an act of homage,
After a few times, she asked me to lick it, which I did with great excitement. Finally I was putting my tongue into her asshole, really rimming her, licking it deeply, penetrating it fully with my tongue. I could sometimes taste her shit a little. We both knew it but we never talked about it--at first.
Then she started to have me lick her asshole when she was on all fours. Having her face away from me, and having her reach back to pull my face into her ass was very degrading. She began making me beg her to be allowed to lick her ass. To tell her out loud that I was her ass licker. I had to tell her I loved tasting her shit. That I wanted to be her toilet. It was very, very exciting.
She told me she was training me to be a toilet slave. That I would learn to love her asshole even more than her cunt. Because that was where I belonged, and what I deserved.