College setting. Our characters are part of the same club (say the Outdoors Club) as a mutual interest. After the mutual meetings they typically hang around and talk together. The boy is interested in the girl and vice versa. The boy is rather quiet though, shy almost, but respectful. The girl reveals she recently lost her virginity to her boyfriend, so the boy while interested isn't about to make the first move. He isn't the type to try and steal another persons girl. He is also a virgin and a bit uncofidant.
The girl, however, isn't that into her boyfriend. She is only 'sorta kinda seeing him' still so is on the look out for some one better. The boy is some one better so sends him an email, asking if he wants to get dinner sometime though she is sorta seeing some one still. A few nights before planned dinner date, she invites the boy over to watch TV. Her room mate is gone. The boy comes over, not sure if the girl is dating some one or just 'hooking' up with them.
While watching TV, she lays down, placing her head in his lap. Its an invitation and the boy boldly leans down to kiss her. They make out and the girl is soon topless on her bed, pulling the boys shirt off as well. Then she moves in for the kill - unbuckling his pants and pulling them down. The boy is naked for the first time in his life with a girl and she is soon sucking his cock, only the second BJ he has ever had. The girl loves giving head - while only having sex with one boyfriend, she uses blowjobs as a means of keeping boys interested in her. And this new boy has a nice hard, thick cock - around 8 inches - and lots of a cum when he busts in her mouth. The boy nervously returns the favor, going down on the girl but needing direction to please her.
((I would go on, but details can be tweaked and fixed as per partners preferences. There will be themes of cheating at one point as well - with her ex boyfriend - so keep that in mind!))