NGOD-293 Flowing Sex: My wife ended up having sex with a man she hadn't even considered... She only intended it to be a one-time thing, but she can't forget the pleasure of that big dick... Airu Sato

"Flowing sex" = sex that just happens. Normally, she would do it with a man she didn't particularly think of as the opposite sex, a man she didn't like or dislike, someone with whom she had a neutral relationship, "just going with the flow of the moment," the atmosphere, the mood. She would just go with the flow, and have sex, thinking, "He asked me, so I guess it's okay." And, unable to forget the pleasure of his big penis, she would have flowing sex over and over again, without her husband knowing.