This isn't sex, but it's kind of a precursor to it. Jacob and Marlena are magically drawn to each other in this scene. Jacob doesn't know why; all he knows is that somehow "she's in my arms" and they're pulled to each other like magnets. Then they dance together, freely and joyously, and Rosie the elephant approves.

When we contrast this description from a young, naïve, and excited Jacob with others that come from the experienced and elderly Jacob, it's actually kind of cute. Jacob is thrilled and overwhelmed by the fact that he's "touching a breast." It's not even a bare breast, but, as Jacob implies, this is still a monumental event in his sexual development.

Jacob's early admiration of Rosie is already setting the foundation for his love for her. This isn't that different from the way his feelings about Marlena grow – from admiration very quickly to love. But unlike in his relationship with Marlena, Jacob can touch Rosie when he wants to (within reason) and doesn't have to hide his affection or worry about the repercussions.