"Thorn"[1]) is a 2014 South Korean romantic thriller film directed by Kim Tae-kyun, starring Jang Hyuk and Jo Bo-ah.

Although he's used to playful advances from pubescent students, things take a dangerous turn when Young-eun (Jo Bo-ah) falls hard for her teacher and daringly confesses her feelings for him.

He called the film "an experiment" due to its eclectic mix of suspense, horror, melodrama and romance, and that his use of cinematography and camera techniques were essential in delivering the "feeling of being trapped."

Wanting the schoolgirl character to embody both innocence and pure sex appeal, Kim auditioned 250 actresses, before casting Jo Bo-ah in her big screen debut.

[2][7] The early working title was Strawberry Milk (Korean: 딸기우유; RR: Ddal-gi U-yu), a drink which Jo's character has a fixation on.