Well, it started like this. I was once married, many years ago. After a few years, our sex became boring and less frequent, something ended. Since I like dancing, we had a few cool places to go to, but my husband was a bad dancer, so I mostly danced alone. Sometimes I danced with a complete stranger, met spontaneously on the dance floor. One day, my husband witnessed my partner start to ostentatiously grope me while dancing, but I didn't let him do anything more. When we got home, my husband told me that he saw everything, but he didn't hold it against me, because he knew I hadn't provoked it. Then he confessed to me that it was a bit of a shame, because he would have liked to see me with someone else and secretly such a thought turned him on. I was surprised, but if that's what he wants, I'm ready to cuckold him, but for fear of being hurt, I'd rather have him nearby.
So the next time we went dancing we sat at the same table pretending we didn't know each other. Shortly after that I picked up a guy during the dance who I liked. After the song he offered me a drink and I accepted and invited him to our table so my husband could witness the situation. After the next dance when we came back the guy asked me what I was doing here by myself and I replied that my husband had upset me and I wanted to have some fun to spite him and then I asked if I could kiss him. He agreed and that was the first time I kissed a stranger right in front of my husband who was calm and just looked at us. After the next dance we went to the men's room where I gave him a blowjob and we fucked. I thanked him for the sex and said goodbye. My husband noticed me leaving and left shortly after me and we went home. In the car, about 10 minutes after I had a stranger's cock in my mouth, he kissed me passionately, saying that the taste of a stranger turned him on. After we got back, we had the best sex in a long time and he didn't even wait for me to wash up after my betrayal.

That was the first time he had become a cuckold on his own accord.