Luna's freedom from Nightmare has been a great relief for Twilight. The worry of Luna's safety while she sleeps gone, but the event opened a new door in her mind.

The kiss shared with Celestia left an imprint on her mind, a yearning she can not hope to quench during her tame playtime with Luna. Celestia wants it as well, the only barrier between her and Twilight the relationship she holds with Luna.

Some fortunate circumstances allow the promiscuous princess an opening.