I thought most indications we've been hearing are that D having multiple partners was to be more from consensus/sharing, rather than at the MC's expense. But, given how her joie de vivre is speeding up and she's becoming more assertive, who knows if a sharing situation could turn into not so much an "open" relationship but be abused and become NTR-ish?
Yeah, that really needs to change, IMHO - she's long reacted to assplay in a positive manner and I bet she can work on the stretching part from now, ongoing. It's time to try putting the MC's thunderstick in D's bottom. Not sure why I'm so invested in this act, but I have a feeling her expressions and squirting-from-anal would be kinda ridiculously hot.