A serial killer ruthlessly hunts down a deaf woman through the streets of South Korea after she witnesses his brutal crime.

A homeroom teacher of Yosan Private High School has an accident, and thus a substitute comes to fill in. Han Bong-Gu is a mysterious man, and after strange occurrences the class president Ye-Rim tries to get to the bottom of this mystery.

Won Tak, Min Joo, Eun Kyung, Chang Kyung, Se Joon, and Se Ra were the best of friends. Inseparable from childhood, they did everything together, sharing every moment of their lives up until the moment they all left for college. Best friends for life, there was nothing this group kept from each other. Or so they thought. Ten years later, the secrets they kept harbored in their hearts come to light, revealing a tangled web of complicated emotions, first loves, and profound friendship. It doesn’t take long to realize even the closest of friends can hide some pretty big secrets.