What's a Little Adultery Between Friends?

Caution: This Erotica Sex Story contains strong sexual content, including Ma/Fa, Mult, Consensual, Romantic, Heterosexual, Wife Watching, Sharing, Rough, Group Sex, Polygamy/Polyamory, Interracial, Black Male, White Male, White Female, Analingus, Oral Sex, Pregnancy, Squirting,

Erotica Sex Story: This is the first part of a likely series, with the theme of "What's a little____ between friends?" I'm not sure if I'll stay alphabetical, but I'm starting that way, with a story about consensual adultery between a man and his best friend's wife, with the full knowledge and approval of the husband, even his participation at times, such as their first encounter, a "devil's threesome."