Amazing party

When I was on holiday in America, I often attend different parties. Almost every party I met one black guy, he had fun, talked with guests, and I never paid him much attention until one day I noticed that he was talking to some guy on the couch, they drank, laughed, joked, and then go to the second floor. I thought that they are gays, and again did not pay much attention to it, but after about an hour this black guy went down from the 2nd floor and quietly left the party, and then a beautiful girl followed him down and also quietly left the party. “Strangely, he go upstairs with the guy and went with the girl” I thought, but did not attach any importance to this.