There is the visual excitement and maybe even the taboo of what is happening.. I consider Stag/Vixen basically wife sharing No one is being forced or degraded.. All parties are aware of conditions (if there are any) in a hetero MFM threesome..
For me a lot is going on in my head.. My normally introverted Asian wife agrees to a threesome with a guy we vetted from a trusted web site we have always used.. Time and date is set at a local hotel.. Wife and I discuss what the "session" might look like days ahead of time.. Her only restrictions, no S&M, no anal and no double vag..
The wife and the other male start off while I get the camera ready.. And this is where it starts.. They start kissing, she'll grab his cock during this, she offers up her tits for him to suck.. Eventually she'll get on her knees and start blowing him.. Keep in mind we just met this guy 20 minutes earlier, and already my wife has his cock in her mouth.. I'm smiling watching this, thinking, "What a sexy slut she just turned into..
She'll get into position for the guy to get at her pussy.. Again in my mind She's offering up her most private, personal body part to be used by this stranger.. She's letting some guy push his dick into her wet pussy.. And it was discussed earlier, no condoms.. So she knows the guy will be pumping his sperm into her and she preparing to receive it..
At some point I step in to get my cock sucked because now my sweet little Asian wife has become a whore working two cock.. I watch as the other guy gets close.. I announce to the wife, "Get ready baby, he going to cum in you".. She'll say "I ready".. Sure enough he cums in her.. Then I tell her, "Hold still baby, I'm putting another load in there"..
It's the watching, as the wife is working both cocks..