Six Crimson Cranes by Elizabeth Lim

Shiori, the only princess of Kiata, has a secret. Forbidden magic runs through her veins. Normally she conceals it well, but on the morning of her betrothal ceremony, Shiori loses control. At first, her mistake seems like a stroke of luck, forestalling the wedding she never wanted, but it also catches the attention of Raikama, her stepmother.

Raikama has dark magic of her own, and she banishes the young princess, turning her brothers into cranes, and warning Shiori that she must speak of it to no one: for with every word that escapes her lips, one of her brothers will die.

Penniless, voiceless, and alone, Shiori searches for her brothers, and, on her journey, uncovers a conspiracy to overtake the throne—a conspiracy more twisted and deceitful, more cunning and complex, than even Raikama's betrayal. Only Shiori can set the kingdom to rights, but to do so she must place her trust in the very boy she fought so hard not to marry. And she must embrace the magic she's been taught all her life to contain—no matter what it costs her.

The Dragons Promise part two