Journey Across the Hidden Islands by Sarah Beth Durst
A story of two sisters. A story of a lion. A story of a dragon.
The sisters are twins. Princess Seika and Princess Ji-Lin are daughters of the emperor of the Hundred Islands of Himitsu. At the age of eleven they were separated. Seika, the older sister remained in the palace and was trained in royal protocol, taught to be a ruler over the kingdom. Ji-Lin, the younger twin was sent far away from the palace to the Temple of the Sun to train as a protector and warrior.
The lion is not just any lion, but instead a magnificent beast with massive wings who serves as Ji-Lin's companion and transport.
The dragon resides of the volcanic island of Kazan and safeguards Himitsu with a magical protective barrier. The sisters must unite to find the dragon and renew a bargain to protect the Hundred Islands. This venture proves more difficult than either girl anticipates and is fraught with unexpected dangers: some serious disturbances in the earth as well as creatures in the form of wild unicorns, mer-minnow, terrifying valravens " and a hundred other monsters, each probably worse than the one before."
Seika "Princesses don't panic. All right, maybe they do a little bit."
"All right. Not going to argue with you about this. But -"