Director Hong Eui-jeong sent a video clip of gorillas to Yoo Ah-in for his character study, asking him for a gorilla-like performance. The video included a outwardly intimidating gorilla eating ants gently and meekly. Yoo said he was impressed by her fresh, new approach to the character.
Yoo Ah-in gained 15kg (33 pounds) and shaved his head for the role. According to director Hong Eui-jeong, the original character in the script was supposed to be a slender man, but in the first meeting, Yoo gained weight because he thought it would suit with the character who worked a lot of physical labor. When Hong, who had expected Yoo's slim young image, was embarrassed, Yoo lost weight in a week. But, Hong was already overwhelmed by his appearance, after their discussions, she agreed that his physical transformation would work well with the character. Then, Yoo began to gain weight again.
The literal English title of this film is "Without a Sound". Hong Eui-jeong titled the script "We Become Monsters Without a Sound like This" at the first.
selected as one of top 12 projects at Venice Biennale College-Cinema 2016/2017
Shortlisted for Sundance Screenwriters Lab January 2016