Beyond the Border Forest: Into the Prawdziwy Las: 1

Two kings rule the ancient woods—the Oak King in summer, the Holly King in winter—and no mortal may cross into their realm without leave. But when eighteen-year-old Rowan Gwózdek’s sister vanishes, Rowan defies the old laws and enters the forbidden forest, desperate to find her.
She isn't alone for long. Keziah, a trans (and very handsome) hunter with a shadowy tie to the Oak King, offers his help—and a perilous path to the Bear Maiden, a creature said to grant wishes. Together, Rowan and Keziah face mossmen, a wood dragon, and other servants of the forest kings.
But danger lurks deeper still. Caught between the warring Oak and Holly Kings, Rowan is forced to take sides in a battle far older and fiercer than she ever imagined. Saving her sister could cost her everything—including her way home.