In Sophie's World, we have one scene that can be described as a sex scene. It's in the chapter 'The Garden Party'; page 478 in my edition. Here's the relevant part:
The guests applauded, and one of the boys threw a firecracker up in the pear tree. Joanna left the table and pulled Jeremy up off his chair. They lay down on the grass and started kissing each other again. After a while they rolled in under the red-currant bushes.
"Nowadays it's the girl who takes the initiative," said Mr. Ingebrigsten.
Having said that, he got up and went over to the red-currant bushes where he stood observing the phenomenon at close quarters. The rest of the guests followed suit. Only Sophie and Alberto remained sitting at the table. The other guests now stood in a semicircle around Joanna and Jeremy.
...fumbling with his belt.
"Don't catch cold!" said Mrs. Ingebrigsten.
Sophie looked despairingly at Alberto.
"It's happening more quickly than I thought," he said.
What is going on in this scene? Why is it important that the girl is taking the initiative? Why does everyone go watch? What is Alberto talking about - what's happening here?