In medieval times, royal marriage was supposedly just a means of forming alliances, so perhaps a princess might be "trained" for this. This alone has a lot of sexy potential, but here's another interesting idea:
"Seduction is just convincing someone to do something they already want to do."
What if the girl is someone who tends to enjoy sex... or bunnies... or whatever the situation calls for. The "training" could just be about her becoming addicted to it. Or perhaps setting up situations for her to discover and explore her preferences? After all, the reader doesn't need to feel guilty about a sexy situation if the girl enjoys it. Fictional characters are convenient like that.
And of course, here are the sources of the thumbnail picture:
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