Hwayi: A Monster Boy is a 2013 South Korean action thriller film about a 16-year-old boy of the same name who is raised by five criminal fathers to become the perfect assassin. It takes pulling the trigger to discover his true identity after he realizes the mystery surrounding his past and his fate. It was the highly anticipated second feature film by director Jang Joon-hwan, a decade after his 2003 cult favorite sci-fi comedy/thriller Save the Green Planet!.

Yeo Jin-goo is a South Korean actor. Yeo began his career as a child actor, debuting in the film Sad Movie (2005). Nicknamed "Nation's Little Brother", he went on to play the younger characters of the lead roles in films and television series such as in A Frozen Flower (2008), Giant (2010), Moon Embracing the Sun (2012), and Missing You (2012). He is known for playing the title character in the action thriller Hwayi: A Monster Boy (2013), for which he won the Best New Actor trophy at the 34th Blue Dragon Film Awards.