A Werewolf Boy (2012) on Netflix

An offer to buy her property brings elderly Kim Sun-yi back to the country cottage she briefly lived in during eventful times in her youth. With her granddaughter by her side, Sun-yi recalls meeting Cheol-su, not only a feral orphan from Korean war days but a mute boy genetically spliced with wolf DNA by a rogue scientist, now deceased. She effectively tames the unsocialized lad through dog obedience training, and he soon becomes more than a loyal companion, protecting her from the rude advances of her late father's business partner's ne'er-do-well, spoiled, self-centered son, Ji-tae, who fully expects Sun-yi to marry him someday. He would claim her as his own sooner than that if not for Cheol-su, who transforms into an unbeatable werewolf anytime someone threatens a member of his pack, leading Ji-tae to work towards a permanent solution to this problem.