Wrath of the Talon by Sophie Kim

The sequel to the "bloodthirsty, addictive, and searingly romantic"* debut from Sophie Kim is an unflinching roller coaster ride of action, romance, and intricate fantasy lore. *Quote from Axie Oh, NYT bestselling author Everyone thinks the Reaper of Sunpo-eighteen-year-old assassin Shin Lina-is dead. The only ones who know the truth are her cherished little sister and Haneul Rui, the icily gorgeous Dokkaebi Emperor, who she was sent to kill ... and kissed instead. Now, with the potent Imugi venom surging in her veins, Lina's returned to right all wrongs. Already her body is changing, growing stronger, stealthier, and more agile, with serpentine scales she can call at will. She is living vengeance, seeking retribution for the massacre of the Talons. She'll become the sword who cuts down the rival Blackbloods gang, along with their ruthless crime-lord leader. And when she is through, she will take the kingdom as her own. But there is a mysterious side to Lina's growing power, a dark voice inside her that whispers and guides her as she slips through the shadows of Sunpo's streets. One that warns her not to trust the Dokkaebi, especially Rui. Because if her destiny isn't to love him ... it must be to destroy him.