You're referring to the 2012 South Korean film "A Werewolf Boy"!
Meanwhile, , a charming but cold government official, arrives in town, claiming to be investigating "wildlife disturbances." He takes a keen interest in Lena’s father’s land, specifically the hunting shack. Lena realizes Thorne isn’t investigating wildlife; he is hunting a runaway subject from a secret genetic experiment—Caleb. a werewolf boy movie
If you are looking for more films that center on a young male's transformation, consider these essential titles: You're referring to the 2012 South Korean film