Some years ago I had a very attractive girl friend she was a little taller than me with slim but curvy figure and beautiful 34D boobs.
When we started having sex together she seemed to enjoy it a lot but no matter what I tried I could not seem to get her to orgasm. Eventually she told me the only way she could cum was by masturbating herself and she asked if that would upset me. Of course the idea did not bother me at all.
Her favorite position was lying face down with her arms both underneath her so she could use her fingers of both hands. She would start fingering and panting while I lay next to her, it was very hot. Then one night she opened her legs a way and told me if I wanted to kneel between her legs and masturbate myself till I shot my sperm between her ass cheeks it would make her own orgasm so much better.
Well I honestly found the experience hotter than I ever thought I would. Even though she would give me really excellent sex in anyway I wanted. Cumming on her ass while she masturbated herself became my most desired sex play with her.