Princess Celestia and the summer of royal waves

"With a class of students about to graduate, the Summer Sun Celebration just around the corner, and a brand-new princess of friendship in her realm, Princess Celestia is more than just a little overwhelmed. Her sister, Luna, suggests she enlist a guest professor to help out during the last few weeks of the academic year, and Duchess Diamond Waves from the land of Monacolt is more than happy to help. Things look great at first, but Celestia soon n...