Wish I had time to write this myself -
Teen boy is visiting his divorced father for the summer. Dad sends him to bed and goes to a bar / adult party / etc.
Hours later, Dad brings a woman home and a girl a year older than the boy climbs in bed with him. "Who are you? What's going on?"
"My mom is playing the kiss game with your dad. I think they're gonna do more. Wanna play the kiss game? Can I kiss you?"
They have a great time kissing most of each other's bodies. He gets his first kiss and the start of his first blowjob. She slowly plays with his dick and asks what he'll give her for more.
Eventually he gives her his prize possession, a handheld video game ( gameboy, switch, or similar) for finishing the blowjob and teaching him to fuck.
Girl leaves with her mom in the morning. Boy loved the experience, but is quite sad she took his game.